Rake
The fee the house takes from each pot, usually a percentage of the pot up to a fixed cap.
Rake is how the venue makes money from poker. In a casino cash game the dealer drops a percentage of every pot — commonly 5% up to a cap of $5–$10 — into a slot before pushing the pot. Some rooms charge "time" instead: a fixed fee per player per half hour. Home games are sometimes raked too, to pay for a dealer, food and drinks, or the host's trouble; plenty of games are rake-free and run on goodwill.
The numbers are bigger than they look. At a $1/$2 game with 5% rake capped at $6, an average pot of $120 pays the full $6 cap. Over 30 hands an hour that's roughly $180 leaving the table every hour — about $18 per player at a ten-handed game. Now compare that to your edge. A very good live win rate is 10 big blinds per 100 hands, which at $1/$2 and 30 hands an hour works out to about $6 an hour. The rake is three times your skill.
That doesn't mean don't play — it means game selection is everything. A rake-free home game against soft players is worth far more to you than a "proper" casino game against the same players. When you review your sessions, record the rake context: where you played, what the cap was, whether there was a jackpot drop on top. A player who beats the game for $12 an hour and pays $18 an hour in rake is a losing player with a winning player's skill. The fix is a cheaper game, not better play.
Two related ideas are worth knowing: rakeback, the partial refund some venues offer, and win rate, which is how you measure what's actually left after the drop.