A computer fan prevents overheating by creating airflow inside the computer case. This airflow helps to dissipate the heat that is generated by the computer's components, such as the CPU, GPU, and memory.

The fan works by spinning its blades, which creates a pressure differential between the front and back of the fan. This pressure differential causes air to flow from the front of the fan to the back. The fan can be positioned to either draw in cool air from outside the case or exhaust hot air from inside the case.

In most desktop computers, there are at least two fans: one to draw in cool air from the front of the case and one to exhaust hot air from the back of the case. Some computers also have additional fans to cool specific components, such as the CPU and GPU.

The speed of the computer is typically controlled by the motherboard. The motherboard will monitor the temperature of the computer's components and adjust the fan speed accordingly. If the components are getting too hot, the fan will speed up to increase airflow and cool them down.

Computer fans are essential for preventing overheating. Without fans, the computer's components would quickly overheat and become damaged.

Here are some tips for keeping your computer fans clean and running efficiently:

• Regularly clean the fans with a can of compressed air. This will remove any dust or debris that has built up on the blades.
• Make sure that the fans are not obstructed by any cables or other components.
• If the fans are making loud noises, they may need to be replaced.