Pot control is a term used to describe an action that result in the pot being kept small because you have a hand that cannot stand a lot of action. Pots are kept small in two ways. The first is to bet smaller because the smaller you bet the smaller the pot size will remain. The second is to check one or two streets. Here are a few examples of pot control:
You pick up Q9o in the cutoff and raise when playing on the Betfair poker website. A decent regular player calls in the big blind. The flop is Q74r and he checks to you and you bet two-thirds pot and the big blind calls. The turn is an off suit deuce and the big blind checks again. Now if you analyse your action here it is going to be difficult to get three streets of value from a worse hand. Your opponent could easily have defended his big blind with hands that dominate yours such as QT, QJ or KQ. By checking back the turn you keep the pot small in relation to the strength of your hand. If he checks back a safe river card then you can go for your second street of value. If he donk leads you can just call. Fans of Betfair poker live should remember this.
The other time you see pot control at work a lot is during live deep-stacked tournament poker. It seems almost mandatory for the play to go check-check on the turn. This is done with the mindset that there is a long way to go in the competition and the wish to steer clear of big confrontations with medium holdings.