A pot in poker consists of all the money or chips wagered by all the players during an individual hand. It is the total sum of all the bets placed from the very start of the hand until there is only the winner remaining.
At the end of each betting round, all money that was wagered is dragged to the middle and added to the pot. If there is no betting action on any street, the pot remains unchanged going to the next street.
For example, with $100/$200 blinds, a player from UTG opens to $600. A player on the button calls and the big blind calls. The total pot is now $1,900 (3x$600 plus the $100 small blind).
On the flop, the button bets $700, and only the big blind calls. That’s another $1,400 going into the pot, bringing the pot total to $3,300.
Tracking the size of the pot is always important, but it’s especially important in pot-limit games, as the maximum bet a player is allowed to make is defined by the pot size.