These are the restrictions on the different types of boards:
Public -- Open to everyone to read and post, whether a member of the site or not.
You must be a member and logged in to Forward Motion (not chat) to post on anything other than the public boards, and you will not even see anything in the restricted or private boards if you are not logged in.
Protected -- Can be read by everyone, but only members can post.
Restricted -- Only members can read and post.
Private -- Only selected members can read and post. (These are mostly the private critique groups.)