Heat elimination is a primary concern for optimizing system reliability. In electronic systems, this can involve one or more heat-transfer modes:
With conduction, hot atoms at the hot side of a solid material move around more than atoms on the cold side. This chain reaction proceeds across the solid and eventually establishes a smooth hot-to-cold temperature variation.
Convection involves a liquid or gas moving past a surface that's either hotter or colder than the fluid. An example is a fan forcing cool air across the hot surface of an IC. The faster the air movement, the better the heat transfer.
As the temperature of a body increases, so does its thermal radiation. When two bodies of different temperature interface with each other, there's a net exchange of radiation from the hot body to the cold, because the hot body radiates more heat.