An Internet forum is a web application for holding discussions and posting user generated content. Internet forums are also commonly referred to as Web forums, message boards, discussion boards, (electronic) discussion groups, discussion forums, bulletin boards, fora (the Latin plural) or simply forums. The terms "forum" and "board" may refer to the entire community or to a specific sub-forum dealing with a distinct topic. Messages within these sub-forums are then displayed either in chronological order or as threaded discussions.

Such forums perform a function similar to that of Usenet newsgroups and the dial-up bulletin board systems that were numerous in the 1980s and 1990s. Early web-based forums such as UBB.classic date back as far as 1996. A sense of virtual community often develops around forums that have regular users. Technology, computer games and/or video games, fashion, religion, and politics are popular areas for forum themes, but there are forums for a huge number of different topics. Internet slang and image macros popular across the internet are abundant and most widely used in internet forums.

Forum is a collection of related topics. When you enter a forum, you will see a listing of current topics in that forum. Each topic contains the original message and, if applicable, replies to that message. As a forum grows, it may be better organized if there were sub-folders. Therefore, a forum can also contain additional forums as well.