Position
Your seat relative to the button, which decides whether you act before or after your opponent. Acting last is the biggest structural edge in poker.
Position is the order you act in on every street. Being “in position” (IP) means acting after your opponent; “out of position” (OOP), before. The difference looks small and is enormous: whoever closes the action decides with all the information on the table, and whoever opens it decides blind.
The seats at a 6-max table
From worst to best: UTG (under the gun, first to act), MP, CO (cutoff), BTN (the button, who acts last on every postflop street) and the blinds, SB and BB, who pay up front and play the whole hand out of position.
Position gets paid in the range
The practical consequence: the worse your position, the fewer hands you can open profitably. In the charts our trainer uses, UTG opens a tight range and the button opens several times more hands — the same J♠T♠ that’s a fold UTG is a standard open on the button. It’s not a style choice: acting last lets you realize more equity with weaker hands.
Train your opens seat by seat in the drill (the engine grades you against the charts) and keep them handy in the printable charts tool.