Active cooling is the use of fans to reduce the heat of computer components. Active cooling contrasts with passive cooling, which involves reducing the speed at which a component is running to reduce its heat.
Typically, a combined approach is used, in which either active or passive cooling is the first option. In power management settings, for example, selecting active cooling means that the system software will increase fan speed to keep the processor at an appropriate operating temperature and will only slow down the speed of the processor if it becomes necessary. Slowing the processor means that system performance will be slower.