Two or more individuals connected to Internet have real-time text-based conversations by typing messages into their computer.
Groups gather to chat about various subjects. As you type, everything you type is displayed to the other members of the chat group.

It is a bit like e-mail in real time. Users have conversations via the keyboard in "Chat rooms" with other users. .
Chat has been criticized for being addictive as well as concerns over unsuitable contact between children and adults.
To join a chat room you usually have to give your e-mail address and this can lead to spam.