Hardware components of the PC
Computer Buses
Expansion cards

An expansion card or adapter is circuitry designed to provide additional functionality to on-board motherboard features. Adapters provide specialised capability, such as video acceleration, sound, or disk drive control, that are plugged into one of the motherboard expansion slots. An expansion card can be divided into two halves, with one half the interface to the system bus, and the other half the interface to its associated device, either integrated on the card or connected to the card.