Definition of pot control
When you do pot control, you are trying to keep the size of the pot small. There are several tricks to pot control. Generally, a player will do pot control with a medium hand or a draw. See below for a concrete example.
An example of pot control
You open A2 in spades on the button and the small and big blind call. The flop comes 6-7-J with 2 spades. Here, in the blind range, there are lots of brelans, 2-pairs, straight draws, etc. After the blinds check the flop, you could bet to make them fold, but you fear the check-raise. If one of the players check-raises you, it will swell the pot to a very large size and if you don't hit the turn, you will be forced to fold your hand. You also don't want to push all in on the flop with a single draw. For all these reasons, you check-back in position with your draw (to make pot control). Afterwards, if a player decides to bet on the turn, the pot will not be out of proportion.
