A fan located inside a computer case attached to the front or back of
the computer that helps bring air into the case and also take hot air
out of the case. Computer
case fans are available in a wide variety of sizes.
 however, 80mm, 92mm, and 120mm (12cm) with a width of 25mm are the most
commonly used case fans in a computer. Below is a graphic example of
what a computer case fan may look like. | 
