How is heat transferred?
Heat is energy transferred between systems because of a temperature difference. Conduction, convection, and radiation are its main transfer mechanisms. Temperature describes a state, whereas heat describes energy transfer; they are not interchangeable quantities.
Three main mechanisms
Conduction transfers energy through neighboring particle interactions and, in metals, mobile electrons. Convection transports energy through moving fluids; density differences drive natural convection, while pumps or fans drive forced convection. Radiation carries energy in electromagnetic waves and does not require a material medium, as in energy arriving from the Sun. All three mechanisms can operate together in one system.
Insulation and everyday examples
Vacuum flasks combine low-conductivity supports, vacuum, and reflective surfaces to reduce different transfer pathways. A surface's cold feel depends on how rapidly it removes energy from the hand, not just its temperature. Heat flows spontaneously from hotter to colder regions; sustained reverse transfer requires external work, as in a refrigerator. Insulation slows equilibration rather than producing energy or eliminating every loss.