Modern network adapter hardware exists in several forms. Besides traditional PCI Ethernet cards, some network adapters are PCMCIA devices (also know as "credit card" or "PC Card" adapters) or USB devices. Some wireless network adapter gear for laptop computers are integrated circuit chips pre-installed inside the computer.
Windows and other operating systems support both wired and wireless network adapters through a piece of software called a "device driver." Network drivers allow application software to communicate with the adapter hardware. Network device drivers are often installed automatically when adapter hardware is first powered on.
A few network adapters are purely software packages that simulate the functions of a network card. These so-called virtual adapters are especially common in virtual private networking (VPN).
