Pot control is a process by which players manipulate the size of the pot based on the relative strength of their hand and the perceived strength of the opponent’s hand. This is done by mixing different bet sizes, flat calling instead of raising, and skipping betting on certain streets.
For example, you open with AK on the button and get called by the big blind. The flop comes A 5 6 with two hearts. You bet, and the big blind calls. The turn comes the 7h. When the big blind checks, you check behind for pot control.
The 7h on the turn is a card that completes many potential draws, so it makes sense to slow down and exercise some pot control in this spot. By betting, you’d be opening the action, giving the big blind player a chance to raise and bloat the pot, putting you in a tricky spot with just one pair.