re: Poker & a 10NL cash game is a 10$ game or a 0.10$ Game?
"Xnl" refers to the value of 100 big blinds, which is a standard buy in for no limit holdem. So, 10nl means $10 which is $0.05/$0.10 no limit holdem, 100nl is $0.50/$1 no limit holdem.
NLHE has a strong element of variance - meaning, luck plays a role. You can make correct plays and still lose the hand. If that happens several hands in a row (which it will), your bankroll will decrease accordingly. Bankroll recommendations exist to account for the fact that even the best players will get their money in good and still lose. It doesn't matter what limit you're playing, so practicing BRM (bankroll management) doesn't need to reference the limit (this is incorrect imo, the better the players are/tougher the limit relative to your skills, the bigger the bankroll you require imo).