A chat room is a virtual place on the Internet where people can get together and type messages to each other using text. People use programs like IRC to join a chat room and type messages or send pictures to the other people within that chat. There are also other programs called instant messengers to stay in contact with friends, colleagues and other people. Websites on the Internet often have types of chat rooms built into them, and lots of chat rooms also use webcams.
Chat rooms are normally used as tools to talk with people that are far away, but many people still use them to talk to people who live near them, because it's very convenient.