Rake in poker is the commission taken by a cardroom (online or casino) operating a poker game. It is normally between 2.5% to 5% of the pot up to a set maximum amount.
Most cardrooms do not take a percentage rake if the hand ends before the flop – this is called ‘no flop, no drop’.
You can normally see the amount being raked as the hand progresses online by a smaller amount than the pot by the dealer – this is taken incrementally by street. Rakeback is a method of rewarding players by returning return part of the rake a player has already played to incentivise them to continue grinding at an online poker room.
Cash game rakeback is either ‘dealt’ (awarded to all players in the hand) or ‘contributed’ (rewarding only the players who have contributed to the pot. The latter is the more common method and generally the rakeback figure is around 30%.
Rake is not necessarily an evil, in fact some professionals argue for more rake in poker.