Immediately apologize for my English, but here's an example:
You are the big blind. Limit $1/$2. The player from UTG raises to $10. All throw, your turn – do you have pocket deuces. Stacks $300.
Set - the path to the big stacks.
In this situation, we will help the potential pot odds. We find it profitable to call this raise to catch a set on the flop.
Imagine that to win a hand is only possible in the case of capture of the set, because you are out of position, and such a hand that went to showdown just not be reached.
You need to call $8 to win $21. Turns out less than 3 to 1 on a call, if using a conventional pot odds. And if we catch a set one time out of eight, it becomes apparent that the call is clearly negative. But if we take in turn the potential pot odds, things will change.
A raise from early position often means a premium hand and positional advantage of your opponent means that after the flop he is likely to be actively set.
So if you did manage to catch the set, your winnings will obviously be more than $21.
This additional income on the following streets, and is a potential pot odds. And if they are above 8 to 1 (chance to catch a set), call the best for a long distance.
Thus, to effectively call $8 on the flop, you must win, on average, $64. The deeper stacks are, the more likely the obtaining of the necessary potential pot odds.