While Facebook can be an excellent way to communicate with friends and family, it can also be the grounds for unwanted interactions. The "Block" feature on Facebook was designed to prevent these unwanted interactions and protects the person initiating the block and the person who is blocked from seeing profile information such as personal updates.
When someone blocks you on Facebook, your name will no longer appear to them in Facebook search results. This works both ways: Their name will not appear to you in Facebook search results either.
When someone places you on a Facebook block list, your name will not show up on friend lists. For example, if you and the person who blocked you have a mutual friend, the person who blocked you will not see your name on that mutual friend's friend list. This works both ways, as you will not see their name on any friend lists either.
When you are blocked, your profile cannot be viewed by the person who blocked you, and vice versa. Even if the person who blocked you has a direct link to your Facebook profile, that link will, instead of going to your profile, generate a message saying "The page you requested was not found."
Unblocking Blocked People
Blocked people can be unblocked via the "Privacy Settings" link on Facebook. At the bottom of the Privacy Settings page is a "Block Lists" option. Click "Edit Your Lists" under this option to block or unblock users.
Limitations of Blocking
Blocking does prevent the majority of Facebook interaction, but does not apply to applications that include games and events. A person who blocked you may still send you requests in Facebook games and invitations to events, and vice versa.