A forum
Forums are the separate themes, help sections, informative places, etc. that you see when you first enter the LEGO Message Boards. You can click on any forum to pick or make your topic and begin posting. You can post and give likes if you have a LEGO ID, but you can browse the forums and topics even if you don't. You could consider each forum as a way to categorize the topics and posts.
Content
Within each of the forums are topics and within those are pages, and some forums even have subforums (and sometimes even sub-subforums) which are smaller forums related to the forum it is in. Each of the topics in the forum is related to the forum it is in, or it is considered spam and the owner will move it to the correct forum or a Moderator will lock and/or delete it. There are 66 forums/subforums. The newest forum to be added was the Disney Princess Forum.