Short for Category 5, network cabling that consists of four twisted pairs of copper wire terminated by RJ45 connectors. Cat-5 cabling supports frequencies up to 100 MHz and speeds up to 1000 Mbps. It can be used for ATM, token ring, 1000Base-T, 100Base-T, and 10Base-T networking.
Computers hooked up to LAN s are connected using Cat-5 cables, so if you're on a LAN, most likely the cable running out of the back of your PC is Category 5.
Cat-5 is based on the EIA/TIA 568 Commercial Building Telecommunications Wiring Standard developed by the Electronics Industries Association as requested by the Computer Communications Industry Association in 1985.