A chat room is an online forum where people can chat online (talk by broadcasting messages to people on the same forum in real time). Sometimes these venues are moderated either by limitting who is allowed to speak (not common) or by having moderation volunteers patrolling the venue watching for disruptive or otherwise undesirable behavior.

Chat systems include Internet Relay Chat (IRC) (where rooms are called "channels"), Jabber, and several proprietary systems on the Microsoft Windows and Java platforms.

Some chat rooms go beyond text messages incorporating 2D and 3D graphics with avatars (these types of systems are also referred to as visual chat or virtual chat). Two examples of 2D chat rooms are The Palace and more recently The Manor (http://www.madwolfsw.com/). These environments are capable of incorporating elements such as games and educational material most often developed by individual site owners, who in general are simply more advanced users of the systems.

Some chatroom sites incorporate audio and video communications, an example of this kind is:Bluesky Chatroom (http://chat.bluesky.com.cn). People may chat in audio and watch each other there.

Lesser known is the UNIX based talker and the French Minitel.

Chatrooms are often confused (especially by the popular media) with discussion groups, which are similar but do not take place in real time and are usually run over the World Wide Web.

Recently much chat room and instant messaging technology has begun to merge as the dominance of the big three instant messaging providers (AOL, Yahoo, and MSN) have tied chat rooms directly into their instant messaging interfaces. This centralization trend is likely to continue to dominate the chat world as these providers begin to merge their services and cooperate in their IM and chat protocols.