Definition: 1. An offensive player who lines up on the very end of the line of scrimmage.
2. A defensive player who lines up on either end of the defensive line.
Examples:
The end on the right side of an offense (for teams with right-handed quarterbacks) is referred to as a tight end, as he lines up close to the offensive linemen. The end on the opposite side is spread out toward the sideline, and is called a wide receiver.