The main role of cabinet fan is cooling system. There are few size are 80mm and 120mm 

with LED and without LED. The three pin fan power connect help to control the fan with the help of control software or mother BIOS. The default airflow system is front to back or front to top or front to down.

Most of the time the LED fan are installed in front side is giving great look for gaming Pcs. Best practice for installation is install with rubber holder will decrease the noise level.