A forum is a piece of software designed to facilitate discussion online. Visitors join the forum to become members and can then post and reply to messages readable by other forum members. Conversations, called threads, are usually visible to visitors but are sometimes hidden from outsiders.
The forum conversation model is not in real time like an internet chat room. This has the effect of making conversations more thoughtful and more focused on the topic at hand, but less personal.
Forums usually have a moderator who monitors posts for inappropriate content and rule breaking. He or she can edit or delete posts and punish offending members with warnings or bans. Each individual forum has its own sub-culture, though there are certain cultural traits that are shared between all forums. For example all regular forum users know what a ban hammer is.
Forums can be a section of a website or a website unto themselves. In a technical sense the code which powers a forum is usually separate from the website code and quite complex. Thankfully, with smart design we can integrate the website and forum so they are aesthetically seamless.
Forums are quite complex coding endeavours, so thankfully there are several off the shelf software solutions which do the technial heavy lifting. One solution for powering forums within WordPress is bbPress. BuddyPress is another plugin for WordPress which provides some of the functionality of a forum, although it is more of an online community in the vein of social networks like Facebook. If you’re not using a CMS, PhpBB is a standalone open source forum.
Other forum software includes:
These examples are all written in PHP.
You can find more information about online forums at these resources: