CHAT is an extension given to files associated with programs for text communication between users in real time. They use the IRC (Internet Relay Chat) network protocol. CHAT files are used to store configuration data about the server, port, and channel name. Channels are popularly called rooms. IRC client programs send messages via the server.

Conversations can take place between two or more users who use pseudonyms for identification, known as nickname or nickname. A popular IRC client is the mIRC program.