It’s basically how many cards can give you the win. ie. you have ace-king and the flop is q-j-7. You need a ten to take the straight. Always assume that all the cards you need are already in the deck. There are 4 tens in a deck so that gives you four outs.

I have a chart that answers all those questions. email me and I will make that available 2 u.

It is basicly a way of finding out the ood of your hand IMPROVING NOT WINNING. Lets say you flop an open ended straight draw. Your holding 7, 8, off suit. The flop comes 5, 6, Q. So any 9 or 4 will give you a straight your hand improves. There are four 9s in the deck and four 4s in the deck so you have 8 (4+4=8) outs to the straight. Take your number of outs and multiply it by 4 and that will give you the % chance your hand will improve.
(8 outs X 4= 32) you have about a 32% chance of hitting the straight. There is a more precise way to calculate the odds but multiplying your outs by 4 is damn close to acurate and yery easy to do.

Lets take that same hand with the straight draw and give us a flush draw as well. You hold 7h,8h the flop comes 5h, 6c, Qh. So you have the same out to the straight as last example but are now holding a flush draw as well. We no there are 13 hearts in a deck of cards and you see four of them. That leaves nine hearts still available.So you have 9 outs to the flush. Add your outs together (9 outs to a flush + 8 outs to the straight = 17 outs). Take your 17 outs and mutiply by 4 and you have a 68% chance of drawing one of your outs and making the flush or straight.

If you dont hit your card on the turn your % odds are cut in half with only one card to come (the river). 68% drops to 34%.

You also have outs to pairs. You could pair up your hole cards 7, 8. You could say you have three outs to a pair of 7s and three outs to a pair of 8s. Not a very strong pair at this point in a game so I wouldent get to excited about them.

Good Luck.

The previous answer was pretty good, except the guy mis-defined “out.” An “out” is a card that will give you a better hand than your opponent’s. So, the implication is that you are behind and must improve to win. Sometimes you think certain cards are outs, when in reality they are not. For instance, you hold As Ks, and your opponent holds Qh Qd. You are behind, but you have 6 outs (an ace or a king will make your hand better than your opponent’s). Now say the flop is:

Qs 10s 10c

You now have a pair of tens, but your opponent has a full house. Maybe you assume your opponent has paired the Q, so you figure another ace, king, or any spade will give you the win (13 outs). However, you are wrong on all counts. You are practically drawing dead since the only way to improve to a winning hand is by catching runner runner AA or KK on the turn and the river. Or you could catch your royal flush with the Js (your only true “out”).