Hardhead said:
What is a tail back? What is a full back? What is a half back? Why are they called half- full- and quarter backs?
A tailback and fullback are usually the same thing, the running back who starts furthest away from the line of scrimmage, although some teams call their half-back a tailback due to the particular offensive formations they use.
A halfback is usually a smaller runner, and in the I formation usually lines up between the fullback and the quarterback, although not necessarily so.
The names for the full-, half-, and quarter- backs date back to an old formation commonly used when football was a new game (but rarely used now) called the "single wing". The descriptions for the positions detailed how far back from the line of scrimmage they were in the formation (a quarter, a half, or the full distance back in the formation).
What are the basic formations? What do they look like, so I can recognize them?
There are dozens of offensive football formations, and only slightly fewer defensive formations. A common offensive formation is the "I" formation, in which the quarterback, halfback, and fullback all line up in a row behind the center. There are usually five offensive linemen, plus a tight end, and two wide receivers in this formation. The "I" is an all purpose formation, used for running or passing. If the quarterback is backed away from the center, and there are fewer running backs, then this is the "shotgun" formation, usually used for passing. There are huge numbers of other formations though, from a power "I" formation (usually used for short yardage running plays, use two tight ends and two running backs) to a five wide receiver set in which the tight end and one of the running backs are replaced by receivers.
On defense, the two basic alignments are the "4-3" and the "3-4", this describes the number of defensive linemen and linebackers in the defense. A "4-3" has four linemen and three linebackers, and "3-4" has this reversed. But there are dozens of other formations, from a "nickel" formation (take out a linebacker and replace him with another cornerback, to better defend against the pass), or even a "dime" formation (two cornerbacks added), and so on.
When is a fullback eligable as a reciever?
Always, as long as he lined up in the backfield.
Why do offensive lines sometimes get called for false starts when one guy twitches, but other people on the line can run around in the backfield?
Once an offensive lineman is on the line of scrimmage and set in his down stance, he cannot move at all until the start of the play. A team can only have one man in motion at the time of the snap, and he is limited in the directions he can more (parallel to and towards the line of scrimmage only), and everyone else must stop completely before the snap (and be seen to be stopped). Any player who is
not a down lineman can be put in motion.
What are the names of the positions of the people doing this stuff?
Players in motion? Running backs or wide receivers usually.