What are "Implied Odds" in Texas Hold'em Poker?
Implied odds or implied pot odds are calculated the same way as pot odds, but consider future betting. You figure implied odds in situations where you expect to fold in the next round if you don't make your draw. You lose no more bets if you miss, but can expect to gain extra bets if you hit the draw.

An example. Say you see the flop with 2 other players acting before you in a NL game. You flop a gutshot straight draw. The first player bets and the second calls and now the pot is laying you 7:1. For a gutshot you want 10:1 or better; however, if you hit your straight on the turn, you stand to stack off one or both of your opponents. Thus your implied odds are considerably greater than 7:1, so you call. 

Implied odds with a flush draw can be dicier. Namely because you can hit your flush on the turn and that kills the action. And your implied odds.

The example is a very simple one. If you were in the same scenario, but 2nd to act instead of last; you would be in a much different situation in that the last player could raise and ruin (or not) your implied odds. Additionally, stack sizes matter. If your opponents are short stacked you may not have the odds for the call. So, when considering implied odds be very aware of the situation.