The total chips bet in the hand.
The blinds and every bet go here, and the winner takes it. Bet sizes are stated as a fraction of the pot. Betting 5 into a pot of 10 is a "½-pot" bet.
At the table
If the BTN, SB and BB each put in 6 preflop, the pot on the flop is 18. A bet of 9 into it is called a ½-pot bet.