A computer's CPU may perform millions of calculations every second. As the processor continues to work at a rapid pace, it begins to generate heat. If this heat is not kept in check, the processor could overheat and eventually destroy itself.
Fortunately, CPUs include a heat sink, which dissipates the heat from the processor, preventing it from overheating. The heat sink is made out of metal, such as a zinc or copper alloy, and is attached to the processor with a thermal material that draws the heat from away the processor towards the heat sink. Heat sinks can range in size from barely covering the processor to several times the size of the processor if the CPU requires it.
Most heat sinks also have "fins," which are thin slices of metal that are connected to the base of the heat sink. These additional pieces of metal further dissipate the heat by spreading it over a much larger area. A fan is often used to cool the air surrounding the heat sink, which prevents the heat sink from getting too hot. This configuration is referred to as a heat sink and fan or HSF combination. While heat sinks are used in nearly all computer CPUs, they have become commonplace in video card processors, or GPUs, as well.