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 convention 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 doe 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