An Internet forum is a forum on the Internet. Purposes for such communities include discussion about politics, gaming, a game in particular, fashion, current events, a television show or series and many others. Forums may also be a conglomeration of many topics, centred around some unifying aspect, such as a parent site. Forums usually focus on textual conversation (while allowing for images), but others, such as 4chan, focus on images to convey meaning.
Each forum has a distinct culture, and may be very esoteric and hard to understand for newcomers (who are admonished to 'lurk moar' when they ask; 'lurking' is the practice of reading posts without making replies or new topics, in order to research the board's history and established precedents). Intra-board history plays a large part in the development of a forum's culture, but inter-forum interaction contributes significantly, as well.