A disc known as the dealer “button” marks who the dealer is for a particular hand.  The cards are dealt in a clockwise direction from the dealer button.  After each hand has been completed  the “button” moves clockwise to the next active player.  This is done because there is an advantage to having to act last and therefore each player will get his fair share of early, late and middle positions.  This player will be considered to be “playing the button" for that hand.