bb=big bets, in no limit holdem it is equal to 2x the big blind. 8bb/100 means 8big bets per 100 hands, which is usually used in reference to your winrate over a certain sample of hands.
.20nl would be .10c/.20cNLHE I assume, but I dunno what site runs .20nl.
For example .01c/.02cNLHE is called 2nl, .02/.05 is 5nl, .10/.25 is 25nl, as you would usually buy in for 100big blinds at least.
@ .20nl that would be $3.20 every 100 hands..BUT people usually use this statistic over a large sample size, 50k hands at the least in order to be accurate. 8bb/100 at anything over 25nl I think would be an impressive winrate, from what i understand.. but use the search feature and look up Wirates.