It is a question and answer section. You ask questions, like you have done up there ^, then other people answer them, like I am doing right now.
If you are used to a forum, it's different to that because instead of lots of messages one after the other, (a) they are ordered by answers with the most votes (i.e. best) and (b) small notes/messages are kept to comments and should be relatively on-topic.
So for example if there are 10 answers and you wanted to reply to the one that is at the top, you would post a comment on the answer, instead of making a post at the bottom like a regular forum.
Hope that helps! Don't forget to check out the rules page for more information.