Originally modeled after the real-world paradigm of electronic bulletin boards of the world before internet was born, internet forums allow users to post a "topic" for others to review. Other users can view the topic and post their own comments in a linear fashion, one after the other. Most forums are public, allowing anybody to sign up at any time. A few are private, gated communities where new members must pay a small fee to join, like the Something Awful Forums.

Forums can contain many different categories in a hierarchy according to topics and subtopics. Other features include the ability to post images or files or to quote another user's post with special formatting in one's own post. Forums often grow in popularity until they can boast several thousand members posting replies to tens of thousands of topics continuously.

There are various standards and claimants for the market leaders of each software category. Various add-ons may be available, including translation and spelling correction software, depending on the expertise of the operators of the bulletin board. In some industry areas, the bulletin board has its own commercially successful achievements: free and paid hardcopy magazines as well as professional and amateur sites.

Current successful services have combined new tools with the older newsgroup and mailing list paradigm to produce hybrids like Yahoo! Groups and Google Groups. Also as a service catches on, it tends to adopt characteristics and tools of other services that compete. Over time, for example, wiki user pages have become social portals for individual users and may be used in place of other portal applications.