Wireless network interface controller

A Wireless network interface controller (WNIC), is a network interface controller connected to a radio-based computer network instead than a wire-based network such as Token Ring or Ethernet.

A WNIC, just like other NICs, works on the Layer 1 and Layer 2 of the OSI Model. The presence of a wireless adapter is fundamental for a wireless desktop computer because it communicates with microwaves by an antenna.
Usually the wireless network interface controller and a desktop computer are connected through a PCI bus.