Pot Odds
The word “pot odds” gives a headache to some players. Most of them recall hearing that they're important, may read an article, don't understand it immediately and eventually give up.
Risk and reward – that's all
If you're talking about stakes it's all about risk/wager and reward/win. Poker is a game that lives of stakes. In order to become a successful player you only have to stake cleverly and to have positive expectation. If you invest 10 euros in a pot, you expect to get more back than that. Otherwise this stake makes no sense. Every time you should consider what you have to risk and what you could possibly win (by the way not only at the poker table...).
Risk and reward at the table
Your goal in poker is to win the pot. This pot consists of bets. Just imagine some situations during a hand. Your opponent bets on the river and you consider either to call or to fold. Or you raise a bet on the turn or you call a raise on the flop.
In all those situations you're investing chips. And why are you investing chips? Exactly! To win the pot. The chips you invest are the risk, your wager and the pot you want to win is the reward. That's it.
The feared pot odds
Invested chips = risk and pot = reward. Doesn't it sound easy? Pot odds are found on this risk/reward ratio. It's nothing more than that.
If you risk 100 euros to win 100 euros, the ratio is 1:1
If you risk 500 euros to win 100 euros, the ratio is 5:1
Vice versa: if you risk 100 euros to win 500 euros the ratio is 5:1, just reversed.
Pot Odds are exactly like this ratio. What do I have to risk to win what?
Pot odds in praxis
There are 500 in the pot and your opponent bets 500. You contemplate a call. What are the pot odds? There are already 500 in the pot and your opponent puts another 500 in it. You can't win just 500, but 500 + 500 = 1000. Your opponent's bet is also part of your potential winnings.
In order to call his bet you have to stake 500. This amount is your risk, the 1000 your reward. The ratio is 1000 / 500, or short 2:1. Thus the pot odds are 2:1.
Supposing you're sitting on the button and everybody is folding to you. The blinds are 10/20 and you think about stealing the blinds. Your potential gain is 10 + 20 (both blinds) and you risk a single raise of about 60. The pot odds for this attempt are 30:60, or 1:2.
Pot odds are absolutely essential. But there's another important part of the game called “the odds”. You won't succeed by knowing only the pot odds. You also have to consider your odds to play poker successfully.
"Poker is a game of people... It's not the hand I hold, it's the people that I play with."
"Look around the table.  If you don't see a sucker, get up, because you're the sucker."
"Nobody is always a winner, and anybody who says he is, is either a liar or doesn't play poker."
"They anticipate losing when they sit down and I try my darndest not to disappoint one of them."