A CPU heat sink is a component in a computer system that is used to dissipate heat generated by the central processing unit (CPU). It is typically made of metal and has a large surface area with fins or other structures to increase heat dissipation. The heat sink is mounted on top of the CPU and is usually paired with a fan to help move the hot air away from the CPU and keep it running at optimal temperatures. This helps prevent the CPU from overheating and potentially causing damage to the computer system.