For every potential action (fold, call, raise) at every point in a game of poker, the correct strategy is influenced by the pot odds facing the player. For example, the lower the pot odds facing a call, the more likely it is that folding will be the correct play, and the higher the pot odds facing a call, the more likely it is that calling is the correct play (to take an extreme example, if you can call for $1 with a $1000 pot, there is essentially no hand that would be correct to fold, because you only have to win one time in a thousand in similar situations for the call to be profitable). Similarly, small pot odds favor bluffing, because they make it less correct for an opponent to call.
Frequently players develop instinct or judgment about the size of the pot relative to their potential bets in various situations and make adjustments, but in some cases it is important to get an exact count. For example, on the next-to-last round of a game when your opponent bets and you are facing a decision on whether to call with a Drawing hand, you need to compare your exact pot odds with the odds of completing your hand (though other factors may be involved as well). Another situation is deciding whether to bluff on the final round: Game theory shows that one should bluff a percentage of the time equal to your opponent's pot odds to call the bluff. For example, in a Pot limit game if the pot is $30 and you are contemplating a $30 bet (which will give your opponent 2-to-1 pot odds for his call), you should bluff half as often as you would bet for Value. With a larger pot, you would bluff less often.