BB = Big Bets which = 2*Big Blind (concept taken from limit poker I think).
So if you play $0.05/$0.10, 10 BB/100 hands is 10*$0.20 = $2 per hundred hands.
If you want to calculate it yourself, take your profit, divide it by however many hundred hands, that equals profit per hundred hands. Now divide this by the Big Bet (twice the BB). So say you've played 500 hands and made $25 at $0.05/$0.10. That's $5 per hundred hands (25/5), and 5/.2 = 25 BB/100 hands.