I am far from an expert and I will use a few examples instead of the technical definition.
You are holding AK of spades in a 3 way pot of $10. The flop is J65 with 2 spades. You are last to act and for simplicity sake lets say both players ahead of you go all in with $5. The pot is now $20 so do you pay $5 to potentially win $20? In this instance yes you do because the chances of one more spade coming out by the river is about 1 in 3. The pot odds are 4:1 ($20 that could be won/$5 must be risked) and your odds of winning is 2:1 (Two times you will miss the flush, one time you will hit the flush). Because pot odds are greater than odds of winning, this is a technically sound play.
I hope that wasn't too complicated, I don't know why I chose such a complex example. So to sum it up, pot odds is what you could win divided by what you have to risk. And that is usually compared with your odds of winning (done by estimating/calculating outs) to make a decision.
You are holding 88 at the button. 5 players call, you call as well. This is a situation where you have great implied odds because you are paying 1BB to see the flop. If you miss you can fold and only lose 1BB which will happen 8 out of 9 times. If the flop is AK8, you have a set of trips and can potentially get paid off much more than the 8BB you lose from calling and folding.
There is more to implied odds but I will let someone with more experience expand on that and explain expectation.