A computer fan is a device used to cool down the internal components of a computer, such as the CPU and graphics card. It works by drawing in cooler air from outside the case and pushing out hot air generated by the components. This helps prevent overheating, which can lead to reduced performance or damage. Computer fans come in various sizes and types, including case fans and heatsink fans. They are typically powered by the computer's power supply and can be controlled by the system's BIOS or software. Proper airflow is essential for maintaining optimal operating temperatures and ensuring the longevity of the hardware.