The advent of the Internet has created more ways than ever for people to exchange information. Two of the biggest forms of online communication are chat rooms and forums, also called message boards. These communication tools are widely used and share a number of similarities and differences. They are essentially similar mediums, with differences that alter the way people use them.
Time: The Biggest Difference
The biggest difference between chat rooms and forums are that chat rooms happen in real time, and forums act as a message system, in which posts are left and can be viewed at a later date or time. If you're not watching and participating in a chat room as it happens, it becomes easy to lose track of a conversation, with the only way to catch up being to scroll up or ask another member of the chat to fill you in. In a chat room, being away for two hours is an astronomical amount of time, nearly equivalent to being away from an active phone call for that long. In the case of message boards, two hours is a very short period of time, especially if the topic or board isn't incredibly active.
Users of Both Mediums
Chat rooms are used more for spur-of-the-moment discussions, while forums act more as a community. With chat rooms, users have the ability to create a room on a whim, change the name of the room later, and flip back and forth between topics without it coming across as strange. Message board screen names ring out around a forum, with certain users becoming known for certain opinions and areas of expertise. Posts are tallied per user, so it's easy to tell who spends a lot of time and energy on the board and who just browses or passes through from time to time. Since the weight of communication is different, the penalties are different for anyone who breaks the rules. In a chat room, if a user is abusive or disruptive, they're kicked out of the chat room and possibly banned for a set amount of time. This may not matter, as the chat room may not even exist an hour from now. However, in the case of a forum, a user could have posted on the board for the last five years, tallied 50,000 posts and become well known around the forum, so being banned from the forum will be a much bigger hit due to the time invested.
Topics: Chat Rooms vs. Forums
Most chat rooms and forums are typically created around a central topic, hobby, lifestyle or interest. Chat rooms are typically more loosely based, with the conversation flowing depending on participants' mood and activity that particular day. Since message boards compile posts for a longer period of time, topics are often responded to in cycles, meaning the conversation can go a number of ways. Forum discussions are laid out by topics, called "threads", so a person can choose to scroll through pages and only participate in the topic or "thread" that interests him. In a chat room, if the current discussion isn't of interest to a reader, he has no choice but to participate, try to change the topic or wait until the topic changes organically.
Private Communication Used
Most chat room clients allow users to veer from the public portion and send users private messages, which like the chat room itself, are instant. The private chat options of forums also mirror their public counterpart, allowing users to post "private messages" or "PM's" to fellow users, which they can read at their leisure. A chat room instant message operates in real time and allows a conversation to continue indefinitely, while forum users have private message boxes, with a finite amount of space, which creates a need to delete messages when the box begins to fill up, much like e-mail.