From the offensive line there are two positions which you will hear being talked about the most and they are the Left Tackle and the Center. The reason for this is that the Center (C) is responsible for snapping the ball to the quarterback which marks the start of the play and the Left Tackle (LT) is responsible for protecting the quarterback on the side of the field he is not facing (otherwise known as the blindside).
The main duties of the offensive line are to protect the quarterback (QB) during a passing play and also to block the defensive players during a rushing play to create space for the running back (RB). The offensive line is split into five positions which are Left Tackle (LT), Left Guard (LG), Center (C), Right Guard (RT), Right Tackle (RT). Please see the Diagram below for how these positions line up at the start of a play: