Cooling Systems
Heat is a by-product of pushing electric current through the various electronic components in the computer. The faster the components work, the more heat is produced. Excessive temperatures can cause the components to malfunction or even damage them. One of the most significant problems with CPUs (and graphics cards is their thermal output. While Intel and AMD are both focusing on making new CPU designs more thermally-efficient, a'' CPUs require cooling. Also, a specific CPU model requires a specific cooling system as some run hooter than others (later Pentium 4s being a good example88).
Heatsinks and Thermal Paste
A heatsink is a block of metal with fins. As the fins expose a larger surface area to the air around the component, a greater cooling effect by convection is achieved. The heatsink is "glued" to the surface of the chip using thermal paste (also referred to as thermal grease or compound) to ensure the best transfer of heat.
A heatsink is a passive cooling device. Passive cooling means that it does not require extra energy (electricity) to work.
In order to work well, a heatsink requires good air flow around the PC. It is important to try to keep "cable clutter" to a minimum.