Position in poker is a matter of the number of players who can still act after you. Playing position is a matter of taking into consideration what those players may do, before you decide what to do yourself.
Position is a mystery to most poker players. But next to the relative value of your hand it is the most important thing for a poker player to think about in the game.
In a poker game you will have bad hands, fair hands, and good hands. The bad hands you will throw away. The very good hands will win for you, but you will not hold them often. The winnings on them will be of great importance only in certain rare cases in which you will be lucky enough to hold a very good hand against a hand that is almost as good, such as four of a kind against a high full house, and remember that such a case can go against you as easily as for you. The fair hands represent the bulk of your winnings and losses, and your success in playing the fair hands will depend very largely on your understanding of position.