Importance of Position in Texas Hold 'em
Position refers to the order in which players act in a hand. It is generally considered that the last person to act has an advantage, since he has more information to work with.
You have position on the players to your right (since you act after them). Players on your left have position on you (since they act after you). Texas Hold 'em is a positional game. Money tends to flow clockwise around the table, hence you want position on the players who are giving a lot and give position to players that aren't taking much.
A simple advantage of acting last is that, for example, by acting last yourself, you have the option to steal or take the free card.
You can play slightly poorer cards if you have position, because you are acting with much more information than any other play. However, it is important that you act on the information you get.
Essentially, with position, it gives you the ability to steal the pot, or at least give you more opportunities to find tells to allow you to maximize your moves.