BuddyPress.org

If you’ve got a system with lots of people, you may very well have more than one person named “John Smith”. That’s why you need unique identifiers like usernames. The regular name “John Smith” then acts like a piece of profile data. This works the same way in WP as in BP, though WP and BP (for a variety of reasons) store that full name info in different places.

The BP-WP profile syncing is basically a syncing mechanism for full names and email addresses. That’s because WP doesn’t have very extensive built-in profiles. On the vast majority of BP installations, users will never have any contact with their WP profile data – all of their profile management will happen through BP, with changes automatically synced back to WP.