Based on PCmag Encyclopedia:
"Also called a "network interface card" (NIC), a network adapter is a plug-in card that enables a computer to transmit and receive data on a local network. Today, the term refers to an Ethernet adapter, although in the past, Token Ring, LocalTalk and FDDI networks were used. A network adapter may also refer to a Wi-Fi adapter (see wireless adapter). Ethernet circuitry is built onto the motherboard of every new desktop and laptop computer, and plug-in cards (NICs) are generally only used in servers and high-end workstations. See Ethernet adapter, Token Ring, LocalTalk, FDDI and OSI model."