sealed bearings are definitely better. they run smoother, spin faster, last longer, cleaner and easier to install. and a 'BB' is an abbreviation of a bottom bracket, that big hole in the bottom of your frame that the crank spindle goes through. a crank what the pedals go on, and the pedal is that square thing that you put your feet on when you ride your bike. i take it you do actually ride/own a bike?