Members of a BuddyPress enabled installation can be connected together by one member adding another as a “friend” and then the other member accepting the friendship request.
Each member will have a visible list of their friends on the site. Friends lists are browsable and members can click on each friend to see more information or add them as their own friend. Profiles are NOT restricted as a whole. Alternatively members can select which information is visible to the general public in finer detail in much the same way your blog is open, but you can make some posts private.
The ability to search for members by username, email or full name will also be included in a “friend finder”.