Button
The button is a marker showing the dealer position, which determines the order of action.
The simple explanation
The button is a marker that shows the dealer position and moves one seat clockwise after every hand. The player with the button acts last after the flop in every betting round, which is the best position at the table. The blinds are posted by the two players to its left.
A closer look
In a casino the dealer does not play, so the button shows who would be dealing in a home game. Position is the most important positional concept in hold'em: the button sees all other players act before making a decision, and it can play more hands and steal blinds. The player on the button pays no blind in that hand. Because the button moves, the advantage is shared around the table.
A practical example
The button moves one seat left after every hand.
Full explanation
The button is a marker showing the dealer position, which determines the order of action.
The button is a disc that marks the dealer position. It moves one seat clockwise after each hand, so every player holds the position in turn.
The player on the button is the last to act after the flop, which gives the best position. He sees what everyone else does before choosing his own action.
The small blind is the seat to the left of the button and the big blind the next one. In heads-up play the button posts the small blind.
In casinos, the disc is often labelled ‘Dealer’. The word is also sometimes used for the player who has it.