This is one of the most rudimentary concepts in poker and it is very important to understand as a beginning player. Poker is played around a table, these days usually with 9-10 people at a table, if we are talking about Texas Hold'em or Omaha (Stud games are 8 handed). The dealer button is ground zero for the deal. That is the perspective from which the hand is dealt. If you are to the immediate left of the button you are the small blind and first to act in subsequent betting rounds to the pre-flop betting. In the first round, since you have posted a blind, you act second last and can opt to call, raise, or fold since you have only got half of the current bet out there. The big blind is to your immediate left. The big blind acts last in the pre-flop betting action, but the big blind (henceforth the blinds shall be written in shorthand, SB and BB respectively) has an option to raise it up in the pre-flop action if no one raised his blind.
Think of the button again as the focal point of the action. This position gets to act last in each betting round. This is a very powerful advantage in poker. The action starts with the player to the left of the button. As players decide to bet, call, raise, or fold, the player on the button has the advantage of seeing what all the other players have done before he makes a decision. Let's say you have a pair of sixes in your hand. There has been a bet, a raise, and two calls when it gets to you. You can likely make a safe assumption that right now you do not have the best hand. If the raise was a large one, you should likely fold that hand. This is not information that the person to your left, in the SB position had when they originally opened the betting.
When the action gets back to that person they have the decision of folding their investment in the pot already, or calling (or re-raising) the raise. Not you. You are getting to make a decision with zero investment in the pot at this point. Compared to the player in the small blind, you are buying a stock today knowing what the price is tomorrow.
As the last player to act, you can also opt to close the betting by calling. No one can raise or re-raise unless you re-open the betting by raising when it gets to your turn. Other players can raise and re-raise of course, but when it gets to you, you can close the betting.
With position in mind, consider your relative hand strength. We are not talking about your grandfather's arm wrestle grip here. We are referring to how strong your cards are as starting cards. The best two cards you can look down to see obviously are a pair of aces. But, that is only going to happen once every 220 hands you play, on average. The worst two cards you can look down and see pre-flop are 72 offsuit. So if AA and 72 offsuit are the poles, which hands should you play? Well, like most things in poker, the answer is 'it depends'. Should you play a mid-pair in early position? That is up to you and your unique style of play. But, we certainly can say without knowing a personal playing style is that having that same mid-pair in late position with a bunch of players now folded, is a better situation that having the hand as first to act. A pair of aces against a full table of players wins just under half the time (if everyone kept their cards for the purpose of the example), but against only one other player it wins better than 4 out of 5 times, again, on average. So, if you end up with AA or a good hand of sorts, the odds of winning the pot with that hand increase relatively to the number of opponents. Like in a football game, you have a better chance of scoring if there is only one defender to beat. Chances of scoring by running all the way down the field and weaving through all the defenders in your way are less. You would prefer fewer opponents between you and the goal. Same goes for poker.
Knowing 'less is more' in terms of opponents, is an important concept. When you have got a good hand, isolate. Isolating your opponents and paring down the field improves your chances of dragging the pot your way.
'Three strikes and you're out' is a common baseball reference. Three outs and an inning is over in a baseball game. In poker, an 'out' is used to refer to the remaining number of cards in the deck that will make your hand. For example, let's say you have KsQs in your hand and the board is Ts-4s-Ad. You need another spade to hit a flush. How many spades are there left? Well, there are 13 of every suit, right? You have two spades in your hand with two of them on the board. So of the known cards, (your pocket cards and the community cards) four of them are spades. That means there are 9 more spades available. Now, people could have folded their pocket spades making them unavailable to hit on the turn card or river card, but... we do not know that. So let's just keep it simple and say there are 9 spades 'somewhere' in the deck. (we could get complicated and say there were probably 3 discarded in the 16 cards that the other players discarded and make an allowance for that in our calculation, but let's not for the purpose of the exercise)
Knowing there are nine spades left, those spades are what we refer to as our 'outs'. Our opponent is betting and we are calling, hoping that we hit one of those remaining spades. We do not know what our opponent's hand is of course, but through his actions we will put him on a hand, that is to say, we will mentally assume he has a specific hand. Based on what he has done, let's say we deduce that he likely has at least an ace in his hand. So he has got at least a pair of aces as his hand. We are drawing here and need to hit one of our spade outs to beat him. We could hit running queens, sure, but we are just going to think about our chances of getting that flush. How many cards are in the deck in total? 52. And again, we know what 5 of them are after the flop. After the turn, we will know what 6 of them are (our two in the pocket and the board four cards). So, before the turn card, what are our chances of hitting a spade? Well, on the turn it would be 9 of the 46 unknowns. 9/46 is .1956. So our chances are 9 in 46, or roughly just under 20%. If we stuck around to the river, we would have an additional shot of 9/45. It might get costly to call though as our opponent will bet to get rid of us and try to scoop that pot right then and there. Unless you have 'the nuts' (the best possible hand) then you do not want to give opponents a chance to draw out on you. In this case, the opponent would not want us to hit one of those 9 spades.
There is actually a simple way to calculate a reasonable approximation of your odds of making that flush, or whatever hand the case may be. It is called 'the rule of 2 and 4'.
Rule of 2 and 4: We just showed how to count your outs. In the case of our flush draw, we have 9 outs. The rule of two and four works like this:
With the turn and river to come still, you have 2 chances to hit one of those 9 outs. Recall we figured out that it was just under 20% or so that we had in terms of a chance to hit that flush with one try. With two tries it is about a 35% chance. With nine outs, on the turn we take our outs and multiply by 4. 4 x 9 = 36. That is pretty close to the actual chance of 35% chance of hitting that flush with the turn and river to come. With just the river to come we multiply by 2. 9 x 2 is 18%. Not far from the actual numerical chance. This is a quick way to come up with your odds and see if it is worth sticking around. The other part of the decision we need to consider is, 'How much money is in that pot?' Why is this important? It is important because if you do not have reasonable pot odds, you should not be calling the bet.
Now that we know how to calculate outs and figure out the chances of hitting the needed cards to make our hand, let us look at the pot itself. Let's say there is $50 in the pot. You are faced with the flush draw situation we just went through and you figure your opponent has a straight. You need to hit that flush to win. Our opponent bets $25. That means there is $75 in that pot now and we have to call $25 to get that. $25 to win $75 is 3-to-1 odds we are getting. What did we say the chances were of hitting the flush in percentage terms? About 19%, based on our rough rule of 2 and 4 calculation for a single draw, but if we stuck in the hand to the river and had another shot that is roughly 36%. 36% is just better than 2-to-1 odds (33.333% being 2:1 of course). So we are getting paid 3-to-1 on a 2-to-1 draw. That is good, right? It is. But as we noted above, the answer to anything in poker is 'it depends'. It is good if he has all his money committed already and we are not liable for another stint of betting which would make it more expensive for us to call on the river. Before acting, consider how situations like this may play out before you commit yourself.
There is another way to look at odds that makes things get more interesting. With pot odds we are assuming no more money is going into that pot when we calculate it out. What if we had some veiled hand that our opponent was not likely to put us on? We might call a long-odds draw in a situation where we figure we will get the pot, AND ALL the chips the player has in his stack if we hit that draw. These are implied odds.
In our example we were getting paid 3-to-1 on a 2-to-1 draw chance. That is good. But what if our opponent had $1500 in chips in his stack? What if the situation was a straight flush draw and not just a flush draw and we think our opponent has trips or something strong he would call with? Maybe we think he has the Ace flush already. We would win if we hit our draw and the straight flush. The pot may have insufficient odds in it to make us think about calling assuming he's got the better of us now. But in some situations, we have to think about the possibility that if we hit our miracle card, we would also get a call from the player for an all-in bet we would make. That makes the odds a lot bigger than what is just in the pot. Whereas above we had a situation where we had to call $25 to win $75, if we hit an open ended straight flush draw and we figured we would get an all-in call from our opponent because he has hit the ace flush, we would have to take his $1500 into consideration as we calculate our odds. Now we would be getting a lot more than 3-to-1 if we hit.