MashGet

Offensive Lineman from WikiPedia:

In American football, each team has eleven players on the field at one time. Because the rules allow unlimited substitution between plays, however, the types of players on the field for each team differ depending on the situation. At the college and National Football League levels, most play only offense or only defense, with "two-way" players being a thing of the past.

The offensive team or offense in football is the team that begins a play from scrimmage in possession of the ball. A play usually begins when the quarterback takes a snap from the center and then either hands off to a back, passes to a receiver or a back, runs the ball himself, spikes the ball, or takes a knee.

The purpose of spiking the ball is to stop the play clock if the offense is running out of time. The purpose of taking a knee is to waste time. If a player runs the ball and stays in bounds, or if a player receives a pass and stays in bounds (this has the same effect as taking a knee), then the clock keeps ticking. But if a player runs out of bounds, or there is an incomplete pass (which also counts as spiking the ball), then the clock stops.

Read more on WikiPedia