An explanation of some commonly used football terms, courtesy of Wikipedia
Dime Defense
The dime defense is a defensive alignment that uses six defensive backs. It is usually employed in obvious passing situations. The formation usually consists of six defensive backs, usually two safeties, and four cornerbacks, and has either four down linemen and one linebacker, or three down linemen and two linebackers.
Nickel Defense
A nickel defense (also known as a 4–2–5 or 3–3–5) is any defensive alignment that uses five defensive backs, of whom the fifth is known as a nickelback.
Wideout
A wideout, also known as a wide receiver or sometimes simply a receiver, is an offensive player whose primary job is to catch passes from the quarterback. He lines up on or near the line of scrimmage where the ball is placed at the beginning of the play, but split to the outside.
Secondary
In football, the secondary is the name given to the group of players that make up the defensive backfield. The defensive backs that comprise the secondary play behind the linebackers, or set out near the sidelines.