This is the odds you are getting when you are drawing, without considering future bets. Basically, if you are drawing to hit your hand, you want to make sure there is enough money in the pot to justify drawing. The way you do this is you calculate your expected value of hitting your hand, which is called pot odds.

The simple mathematical formula for pot odds is:

(pot + bet) * (chance of hitting) >= bet

For example, say you have a flush draw of diamonds. You are fairly certain you will win if you hit the flush but will lose otherwise. Thus, there are 9 other diamonds out there (13 - your two, - two on board), so you have a roughly 19% chance of hitting a flush on the next card. If the pot is 90, and the bet is 10, you have odds with your flush draw.

(90 +10) *.19= 19
19>10, so you should call

However, lets say the pot is 10, you're at the turn (one card left) and your opponent bets 40. So the pot is 50 (including his bet) and the bet is 40 to you.

(50 + 40) *.19= 17.1
17.1 < 40, so you should fold.