what are expansion slots

Expansion slots are connections or ports inside a computer on the motherboard or riser card that provide an installation point for expansion cards. An expansion card is a printed circuit board that can be inserted into an electrical connector or expansion slot on a computers motherboard to add functionality to a computer system. Expansion slots allow the capabilities and interfaces of a computer system to be extended or supplemented in a way appropriate to the tasks it will perform. The most common types of expansion slots are AGP, PCI, and PCI Express. The number of expansion slots a computer has depends on the form factor of the case and motherboard, but generally, a computer system can have anywhere from one to seven expansion slots. Expansion cards can provide various functions including sound, modems, network, interface adapters, TV and radio tuning, video processing, host adapting such as redundant array of independent disks or small computer system interface, solid-state drive, power-on self-test, and more.