PCI defines the electrical characteristics and signal protocol used for two devices to communicate over a computer's central bus. PCI network adapters and other devices exist in several different shapes and sizes called "form factors."
Besides traditional Ethernet PCI cards that manufacturers pre-install inside desktop computers, common PCI form factors for consumer network devices are:
- Card Bus - either Wi-Fi or Ethernet PC Card (also known as PCMCIA or "credit card") network adapters
- Mini PCI - Wi-Fi network cards embedded inside notebook computers