What does a wireless card do?

a "wireless card" is a network card that receives a high frequency signal from a wireless router or wireless access point. Same as an Ethernet Card/Network Interface Card(NIC), only wireless.

A wireless Card is a network card which connects to a radio-based computer network, unlike a regular network interface controller (NIC) which connects to a wire-based network such as token ring or ethernet. A wireless Card, just like a NIC, works on the Layer 1 and Layer 2 of the OSI Model. A wireless Card is an essential component for wireless desktop computer. This card uses an antenna to communicate through microwaves. A wireless Card in a desktop computer usually is connected using the PCI bus. Other connectivity options are USB and PC card. Integrated WNIC's are also available, (typically in Mini PCI/PCI Express Mini Card form).