I do not understand it. So what do you do when you become a ubb buddy? Do you talk? Don't you do that anyway on the board and through PMs? How is this buddy business different?

No idea. I don't know if anyone has ever done it.

my "buddy list" is empty, but I think the way it works, if you add people to your list, you can select one (or more) from your list by 'checking' a box(s) and then send a PM to that selection. it would really only seem to be useful if you want to send a single PM to multiple "buddies". (e.g., special season's greetings; personal stuff you wouldn't share with the world)

HNY,E.
ETA: (It's called acronymical language - ICAL)