What do favorites do?

Besides sharing your favorites with others what does it do?  I don't see a My
Favorites link anywhere. 

A Favorites tab is located on your user profile panel, it's a way to keep track
of favorite posts, forums and users for easy and quick reference.  You can also
view other members' favorite users, posts and forums if they have enabled the
"Share favorites" option in their profile.  You must enable the
"Share favorites" checkbox in your profile to allow others to view
your favorites.

If you really want to get into favorites, Community Server MVP Keyvan Nayyeri
has written a developers guide on Favorites.