In the upper right hand corner is a green "tab" that says "help". It leads a page where you can find FAQ's, Open a Support Ticket, and other "helpful" things. The HELP tab is just to the left of the "Community Tab" that leads to this board.
When you block a person, they can no longer invite you to a private message or post to your profile wall. Replies and comments they make will be collapsed/hidden by default. Finally, you'll never receive email notifications about content they create or likes they designate for your content.
Note: if you proceed, you will no longer be following .