Poker rake is a fee from the live poker or online poker room to players. This is generally how they generate revenue. There are different types of poker rakes. The most common type is the pot rake.
During cash games, a small proportion of the pot is removed by the dealer upon the completion of a hand. Poker networks differ in exactly how they do this, but it is normal for no rake to be taken from the pot unless the hand makes it to the flop. If a player raises pre-flop and everyone folds, no rake is taken. Generally, a typical amount for this type of pot rake is between 5 and 10 per cent of the total pot size in cash games.
Some real money casinos use the dead drop, to ensure everyone pays the same rake. The player on the button pays an agreed fixed amount rake to the dealer before the hand begins.
As an alternative to the above and a policy that applies to brick and mortar casinos is timed collection.
This is where a fixed fee of the rake is collected, for example, every 30 minutes from all players. Timed collections and dead drops are less common and most of the online poker sites use the pot rake method. Which is universally understood by all cash game players.
In most legal jurisdictions, taking a rake from a poker table is illegal if the party taking the rake doesn’t have the proper gaming licenses or permits. The gambling laws in many jurisdictions do not ban poker players in a private dwelling, provided nobody takes a rake.