Before any cards are dealt in Hold'em, two players have already put chips in the pot. They did not choose to; the seat did it for them. These forced bets are the blinds — blind because the players post them without seeing a card — and without them the game does not work at all.
Why the game needs them
Imagine a table with no forced bets. Nobody has anything at stake, so nobody has a reason to play a hand that is not near-perfect. Everyone folds until someone is dealt aces. The game grinds to a halt, and the one player who does bet gets no callers. The blinds fix this by putting something in the middle to fight over on every hand. Whatever you are dealt, there is already a pot, and folding costs you your share of it.
Who posts them
The dealer button marks a seat and moves one place clockwise after each hand. The player to the button's left posts the small blind; the next player posts the big blind, usually twice as much. At our tables you will see the badges on the seats. Because the button moves every hand, every player takes a turn paying the blinds, and over a full orbit the cost is the same for everyone.
The blinds also set the scale of the game. The big blind is the minimum bet, and stack sizes are usually described in big blinds — a 1,000-chip stack at 10/20 blinds is fifty big blinds, a comfortable amount; the same stack at 50/100 is ten, which is desperate.
The order of action before the flop
Because the blinds have already bet, the first player to act pre-flop is the one after the big blind. The action goes round to the small blind, who must add the difference to stay in, and then to the big blind — last.
The big blind's option
The big blind has already put in a full bet. So if everyone else just calls, the action reaches the big blind with nothing to call — and they get a choice nobody else got: check to see the flop for free, or raise. That raise is the big blind's option, and it is why posting a blind is not the same as acting. At our tables the option is always kept: after a round of limps, the big blind's buttons show CHECK and RAISE, never a forced call. The rules behind which buttons appear are in check, call, bet, raise.
After the flop, the order flips
From the flop onward the small blind acts first and the button acts last, on every street. Being last is a large advantage — you see what everyone else does before committing — and it is why the button is the best seat at the table and the blinds are the worst. That is the subject of poker position explained.
What the blinds ask of you
Two things. Defend them sensibly: the chips you posted are already the pot's, not yours, so do not call a raise with a bad hand just because “you are already in”. And steal them when you can: from the button, a raise into two players who have to act out of position will take the blinds uncontested often enough to be worth it with a wide range of hands. The blinds are a tax on sitting still. The game rewards the player who treats them as a target instead of a fee. The full structure of a hand is in how Texas Hold'em works.
