Because most versions of Hold 'em played in a poker room (real and virtual) have a dealer that's employed by the house, a rotating disk ( the "button") designates which player gets to act as the dealer for the hand, even though they won't touch any cards but their own. The reason why the poker rooms go to all this trouble of designating the dealer for each hand is because from a strategic point of view, the dealer's spot is the best. Of course, the dealer "button" rotates around the table so that each player has an equal opportunity to act in the dealer's position; basically once every 9 or 10 hands, if you're at a full table.
The advantage of being the dealer is that you get to act after all the other players, except in the pre-flop betting, where you still have position on everyone other than the Small and Big Blinds. This position advantage is significant for several reasons:
To me, the best part about playing on the button is that I can, from a mathematical point of view, play more hands profitably. What might be a wasted bet "under the gun" can be profitable when made from the button position. For example, one of the most popular hands of all, J -10 offsuit, is highly over-rated as a starting hand in early position (and, in fact, should be folded), but it does become slightly profitable on the button. The saving grace is that this hand makes a lot of Straights, but it's usually a loser if that doesn't happen. Even so, if several players ahead of you "limp" (just call) into the pot, the hand of J-10o is certainly worth one bet. With a lot of players, it usually takes a hand like a Straight to win the pot, so from the button, J-10o is frequently worthwhile to play. Of course, one of the Blinds may raise, which will make the J-10o a fold, but that's poker. If you wanted guarantees, you would be at some life insurance site, not here.
While it's really a topic that deserves its own lesson, stealing the blinds is a lot easier when you're on the button. Don't kid yourself, though. A lot of players almost expect a raise from the player on the button - it's known as a "position" raise - so you can get burned if you do it too often. However, with a decent, if not great, hand that you'd be playing anyway, a well-timed raise is warranted and it may pay off if the Blinds have demonstrated that they're prone to folding. At the best, you may win the pot right then and there, but if not, perhaps you'll drive some trash hands out of the game, which may give your hand a better shot at winning. At the worst, you'll get reraised by one of the Blinds, in which case you should refer to the chart I'll be presenting for how to play the hand at that point.
But before I do that, let's look at the idea of concealing a big hand when you play it from the button. Generally, in low-limit hold 'em games a raise from an early position sends a signal that you have a "big" hand, so most will fold behind you - which is not all bad - but it does tend to cut down on your earnings. However, if you do that same raise from the button, many players will think it's the "position raise" I mentioned earlier, so they might call, which is lovely. Of course, if you get re-raised, all the better. When it gets back to you, reraise if appropriate and you're now involved in a "monster" pot with probably the best hand.
It's obvious that being on the button has its advantages, but it's not a license to play trash like J-6o, 10-5s and so forth. You still need to play decent hands here, but a lot more hands will qualify as "decent", so it's definitely a place where you can make some $$$. One more point: If the player to your immediate left is inclined to fold a lot, then you should look for opportunities to "buy the button." What this means is that even after the button has moved to this person, you may want to raise as though you were still on the button yourself, because if you can get this person to fold, you'll be the last to act during the hand after the Blinds have played. Of course, if this player - who can be described as "tight" - raises you back, it's probably time to fold. But, once again, my chart will show you how to react. Okay, here's the chart and you'll see that it follows the same format as the others, which is to list the minimum hands needed to bet from the button. The options you have are usually to raise or reraise, call or fold, just as I show in my other charts. What I want to stress is that this chart is appropriate for limit Hold 'em games and, like most of my others, will make you appear as a "tight" player, which may or may not suit your style of play
(Source: GameMaster)