Guests - anyone can start new message threads or reply to messages in existing threads. You will need to match a pattern of letters and numbers to prove you are not a spam bot. This is similar to technology used by Blogger™.
Members - If you register to become a member, you will be asked to provide a username (not your real name - for privacy purposes), and you will be sent an email, to which you must reply to prove you are not a spam bot. You will then be given the opportunity to create a user profile where you can put information about yourself for other members to see, and even upload an avatar (a little picture to represent you on your messages). Once you reply to the email, your membership will be activated automatically. You can then view other member profiles, get info on which members are currently in the Forum, or have stopped by during the current day, and you can even request email notification of replies to any subforum or thread (just click on "Advanced Options" under the last message in the thread you are viewing).
Moderators and Administrators - Well, that's just between us for now.
Formatting - The best way to learn the formatting system is to use the buttons at the top of the "Add post/Edit post" form. When you're ready use the "Preview" button at the bottom of the form to see if things came out the way you wanted. If not try editing some more. When you're satisfied click on "Save Post," and you've done it!
The "Add Poll" link enables you to add a poll to your post. Normally this consists of a question you make up, and several possible answers.
For whatever isn't obvious try the "Help" link. The one thing that might be tricky is putting in links to other pages. The format is
[url=http://www.yourlink.com]Your Link Title[/url]