Quarterback – sometimes called signal caller – he’s the one right behind the line of guys up front and he gets to start the play. He’ll either hand the ball to a running back, pass the ball to a receiver, or run it himself. Or he’ll get sacked by the defense – which is a good thing if he plays for the other team!
Running back – sometimes called halfback or tailback – usually the guy the farthest behind the quarterback. He’ll either be handed the ball to run with it, or he’ll go out for a pass. He may just stay in the backfield and block for the quarterback – though a lot of running backs are terrible at blocking.
Some teams still use a fullback, a guy who usually blocks for a tailback, but these guys are becoming more and more rare. They also sometimes run the ball when short yardage is needed.
Wide receiver – sometimes there are more than one – they typically line up at the end of each side of the offensive line and go out to catch passes. You sometimes see them moving before the ball is snapped and that’s OK. They’re usually the faster guys and if they’re tall, that’s even better so that the quarterback can throw them a high pass that a short defender couldn’t reach.
Tight end – usually lines up at the end of the line that’s bending over with a hand on the ground. The tight end stays on the line and blocks, or goes out for a pass – though usually not long passes.
Now for the offensive line:
Center – the guy in the middle that holds the ball on the ground is the center. He needs to be very good at getting the ball to the quarterback and then blocking the guy in front of him. Not as easy as it sounds.
Guards – the guys on either side of the center are known as right guard and left guard. Their job is to block the defensive guys that are trying to get through the line to get to the quarterback or running back. They’re usually very large and don’t have to be too quick – but it helps.
Tackles – the guys next to the guards are known as tackles (and have become quite famous through the movie “The Blind Side”.) For right handed quarterbacks, the left tackle is the most important one and for left handed quarterbacks, they favor the right tackle. Tackles are usually very big, but they have to be quick so that they can block the defensive guys coming off the end of the line.