What is Bitcoin?

Bitcoin is an open-source digital money and payment network that is not managed by a central bank or a single company and enables peer-to-peer value transfer over the internet. The network's native asset is known by the symbol BTC; its smallest unit is the satoshi, and 1 BTC can be divided into 100 million satoshis. Transactions are recorded on a public blockchain validated under shared rules by computers around the world. Bitcoin's price can be highly volatile; losing a private key, sending to the wrong address, fraud or the collapse of a custody service can cause permanent loss. This content is for general information and is not investment advice.

Bitcoin's origins, operating system, blockchain and mining

1. What exactly is Bitcoin? Bitcoin is both a peer-to-peer electronic cash system and the digital asset called BTC that is used in that system. It is not held in the database of a single organization like a bank-account balance; independent nodes on the network inspect valid transactions and blocks under the same consensus rules. Its software is open source. No company can by itself issue new Bitcoin, arbitrarily erase a valid transaction or unilaterally change the network's rules. Users may nevertheless rely on centralized intermediaries such as exchanges, payment companies or custody services. 2. Who created Bitcoin? Bitcoin's design was described by the person or group using the pseudonym Satoshi Nakamoto in the technical paper ‘Bitcoin: A Peer-to-Peer Electronic Cash System,’ published on October 31, 2008. The network began operating when the genesis block was mined on January 3, 2009, and the first software was released shortly afterward. Satoshi's real identity is not known with certainty. Bitcoin today is not a product directed by one founder; it is a distributed ecosystem of users, developers, miners, node operators and service providers. 3. What is a blockchain? The blockchain is Bitcoin's ordered, timestamped and public record of validated transactions. New transactions are gathered into blocks. Because every block links to the previous block header's hash, changing an old record also requires rebuilding the blocks after it. Full nodes independently validate blocks they receive and accept only the chain that follows the rules. The blockchain's openness means address movements can be seen; the protocol does not require the real person's name behind an address to be written there. 4. How does a Bitcoin transaction work? Bitcoin uses unspent transaction outputs, known as the UTXO model, rather than account balances. A transaction spends eligible outputs received earlier as inputs and creates new outputs for recipients. The sender produces a digital signature with the relevant private key to prove spending authority. Nodes check the signature, whether the inputs have already been spent and whether the transaction follows the other rules. When the sum of inputs is higher than the outputs, the difference may become the miner transaction fee. 5. What are a Bitcoin address, public key and private key? A Bitcoin address is an identifier derived from public-key data and shared to receive payments. A private key is secret information that allows particular Bitcoin outputs to be spent. You may share your address; you must not share your private key or recovery words. Anyone who obtains the private key may be able to transfer the related assets irreversibly. Owning Bitcoin does not mean holding a physical coin; it means controlling the keys capable of spending outputs on the blockchain. 6. What is a wallet? A Bitcoin wallet does not put coins inside a file; it generates and stores keys, calculates balances and signs transactions. Mobile, desktop, hardware and online custody wallets are available. In a custodial wallet the service provider controls the keys, while in a non-custodial wallet the user does. A hardware wallet can help isolate a key from an internet-connected device, but it does not eliminate the risks of a counterfeit device, a faulty backup or user error. Wallet choice should reflect the amount, frequency of use and the user's security knowledge. 7. What are recovery words for? Many modern wallets provide a recovery phrase, often 12 or 24 words, from which many keys can be regenerated. These words are the wallet's backup; photographing them, uploading them to the cloud, sending them in a message or entering them on a website creates serious risk. A person or website asking for the words may be fraudulent. The backup should be kept offline and securely with fire, water, loss and unauthorized access in mind. If the recovery phrase is lost, the wallet company may not be able to restore access. 8. What is mining? Miners form candidate blocks from pending transactions and perform many calculations to find a result that puts the block header hash below the network target. This proof of work makes altering earlier blocks costly. The miner that finds a valid result may claim the block subsidy and the transaction fees included in the block; other nodes validate it. Being a miner does not grant power to change the rules: nodes reject invalid blocks even when computing work was spent on them. 9. Why are proof of work and difficulty adjustment needed? Proof of work helps participants who do not know one another agree on one transaction history and makes it difficult to spend the same Bitcoin twice. As the network's total computing power changes, mining difficulty is adjusted every 2,016 blocks; the goal is for blocks to form about once every ten minutes on long-term average. Short-term block intervals may be random. A party attempting to alter an earlier transaction must also catch up with the work in the later blocks. 10. Why is Bitcoin's supply limited? New bitcoins are created through the block subsidy under a predetermined schedule. The subsidy is cut in half every 210,000 blocks, roughly every four years; this event is called the halving. The rules limit total issuance to about 21 million BTC, with the final fractions expected to be mined around 2140. Coins that cannot be spent because their keys were lost may reduce the usable circulating amount. Limited supply does not guarantee that the price will rise; price depends on demand, liquidity, regulation, expectations and market conditions.

Payments, fees, privacy, security, risks and frequently asked questions

11. What do confirmation and settlement mean? When a transaction is broadcast to the network, it may first wait in nodes' temporary transaction pools. It receives its first confirmation when a miner includes it in a valid block; every later block built on top raises the confirmation count. More confirmations increase the work required to reverse a transaction, but the protocol has no single magic safe confirmation number for every amount and situation. Small payments and high-value commercial transactions may use different risk policies. A transaction that has not entered the chain should not be treated as a settled payment. 12. How is a Bitcoin transaction fee determined? The fee depends more on the transaction's data size in a block and demand for block space than on the amount of money sent. A transaction spending many UTXOs can be larger and require a higher fee. Users can choose a fee rate; miners generally select transactions offering a higher fee per unit of data first. During high demand, a low-fee transaction may wait a long time. Some wallets support methods to raise the fee or accelerate an eligible transaction with another transaction. 13. What is the Lightning Network? The Lightning Network is a second-layer approach that processes frequent, small payments through payment channels outside the main blockchain and later carries the results to the Bitcoin chain. It can provide faster payments at lower fees. It also introduces additional concepts and risks involving channel opening, liquidity, online availability, routing and the custody model of the wallet used. BTC on Lightning is not a separate coin; the system is built on Bitcoin transactions and smart-contract-like conditions. 14. Is Bitcoin anonymous? Bitcoin is pseudonymous, not fully anonymous. Although names do not appear in addresses, transactions are public and movements between addresses can be analyzed. Exchange identity information, address reuse, IP data or payment context can connect an address to a real person. Using a new address for each payment may improve privacy but does not guarantee complete secrecy. Anonymity should not be relied upon to avoid tax or legal obligations. 15. Is the Bitcoin network secure? Bitcoin's security does not rest on one password; it relies on digital signatures, hash functions, proof of work, economic incentives and independent rule validation by nodes. Rewriting a long transaction history requires substantial computing and energy cost. Network resilience, however, does not mean every user account is secure. Phishing, malware, fake applications, SIM swapping, exchange failure, weak passwords and stolen recovery words are more common causes of loss. 16. Can Bitcoin transactions be reversed? There is no central bank or customer service able to cancel confirmed Bitcoin transactions. BTC sent to the wrong address or transferred to a fraudster usually cannot be recovered unless the recipient voluntarily sends it back. Checking the first and last characters after copying an address, confirming the network type and sending a small test before a large amount can reduce risk. Do not rely only on the pasted result because malware may replace the address shown on screen. 17. What are Bitcoin's main uses? Bitcoin may be used for local or cross-border value transfer over the internet, payment for some goods and services, donations, long-term savings or speculative investment. Use depends on merchant acceptance, national law, tax rules, fees and technical infrastructure. Bitcoin does not have legal-tender status in every country and does not guarantee price stability. Calling an asset ‘digital gold’ does not make it legally or economically identical to gold. 18. What are Bitcoin's main risks? The price can rise or fall sharply in a short period and an investment can be lost in full. Transaction errors may be irreversible, loss of a private key may be permanent, and a custody service may be hacked, cease operating or block withdrawals. Fake investment platforms, guaranteed-return promises, social-media impersonators and recovery-service scams are common. Regulation and tax rules vary by country. Trading with debt, emergency funds or money one cannot afford to lose magnifies financial harm. 19. How is Bitcoin stored and what basic security measures apply? It may be sensible not to keep a small daily-use amount and a large long-term amount in the same place. A wallet should be downloaded only from an official source, devices and applications kept current, and a strong unique password and authentication used where possible. Recovery words must never be given to staff, entered into a web form or stored online. For large amounts, backup planning, inheritance access, hardware wallets, multisignature arrangements and a small test transaction first may be evaluated with specialist help. 20. What is the difference between an exchange and a personal wallet? For Bitcoin held on an exchange, the private key is usually controlled by the exchange; the user trusts its account and withdrawal system. In a personal non-custodial wallet, the user controls the key and intermediary risk may fall, but backup and transaction-security responsibility passes fully to the user. The saying ‘not your keys, not your coins’ highlights custody risk, but self-custody also requires knowledge and discipline. No single method is safest for everyone. 21. Are Bitcoin and other cryptocurrencies the same? Bitcoin was the first widely operating decentralized cryptocurrency network; other crypto assets may have different supply, governance, consensus, programmability and trust models. A token existing on the Bitcoin blockchain or another chain does not make it Bitcoin. BTC is the Bitcoin network's native asset. A similar name, logo or ‘Bitcoin-backed’ claim is not proof of technical equivalence; the contract address, network and custody method must be checked separately. 22. How does Bitcoin affect the environment? Proof-of-work mining consumes electricity; its environmental effect depends on the amount and source of energy used, hardware lifespan and local grid conditions. Renewable energy can reduce emissions but does not reduce energy use to zero. Using stranded or curtailed energy may be beneficial in some circumstances, while fossil-fuel generation and electronic waste can have negative effects. Evaluation should consider not only total consumption but also the energy mix, emissions and opportunity cost. 23. Can Bitcoin's rules change? Bitcoin software can be developed, but a new rule becomes effective on the network only when users and economic actors run it. Backward-compatible restrictions are called soft forks, while changes incompatible with old rules are hard forks. A developer writing code cannot compel the network alone, and a miner cannot make nodes accept a block they reject. Separate networks may form if groups cannot agree. This distributed process reduces central control but can make change slow and complex. Frequently asked questions ‘Is Bitcoin physical money?’ No; it is represented in the protocol by digital transaction records and keys. ‘Do I have to buy 1 Bitcoin?’ No; BTC can be divided into small units. ‘Does owning Bitcoin make me anonymous?’ No; the blockchain is public and identity linkage may be possible. ‘Can a Bitcoin transaction be canceled?’ There is no central cancellation mechanism for a settled transaction. ‘Are all 21 million bitcoins circulating today?’ No; issuance continues over time and some coins may be lost. ‘Will the price definitely rise?’ No; limited supply does not guarantee price appreciation. ‘Is buying Bitcoin risk-free?’ No; it carries high volatility, custody, fraud, technical and regulatory risks. Source basis: Satoshi Nakamoto — Bitcoin: A Peer-to-Peer Electronic Cash System; Bitcoin Developer Guide — Block Chain, Transactions and Wallets; Bitcoin.org — You need to know. Sources checked on October 19, 2026. This text is not investment, legal or tax advice.