To show how differently you have to play in first and last positions, let's say I'm dealt in no-limit hold 'em (where position remains fixed throughout the hand). If the opponent on my left raised a moderate amount and got three calls, I would also call as long as most of the players had a decent amount of money in front of them. Were I to flop three 6s (the odds against it are about 8-to-1). I'd anticipate winning a big pot. However, were the player on my right to raise the same amount. I'd have to fold my pair of 6s even if I thought there would be some calls but no raises behind me.

My bad position is what makes the difference. It changes things enough on future rounds to turn a call into a fold. If I were to flop three 6s in last position, that 6 on board would look pretty innocuous. The original bettor would probably bet again, maybe get called, and then I could put in a big raise - or perhaps slowplay and wait to raise on fourth street. However, if the bettor were to my right, I couldn't immediately raise with three 6s and hope to be called by players behind me whether on the flop or on fourth street. Thus, when I'm directly behind the bettor, my implied odds are reduced so much that it's not worth calling that bettor's first raise before the flop.

Position is important in relation to the playing style of the other players in the game. You prefer having the loose, aggressive player in the game sitting to your right and the tight, conservative player to your left. Then you can usually decide how to play your hand after the aggressive player has acted, while you don't have to worry about many surprises from the conservative player behind you. You are also in a better position to control the aggressive player and indeed to trap him into mistakes. Similarly, if there are players in the game who tip off whether or not they are playing a hand, you'd like them to your left so you can use that information when deciding whether to call the first bet yourself.In sum, while in a horse race you like being first, in a poker game you like being last.