Can someone explain (sorry, very basic question)

[maven]

Originally Posted by SamG

Thanks for the answer. I guess what throws me off is when you see (generally) a lineman "flinch", and the flag is thrown.

That's a foul for false start because the lineman has simulated the snap. Teams that look to the sideline for the play have to be careful not to jerk up in their shifting, or they risk being flagged for FS.

The shifting you saw Louisville do involved backs (including receivers lined up off the line of scrimmage) and ends only. But by rule all 11 on offense are permitted to shift, and to do so as often as they wish within the limits of the play clock.

Before snapping the ball (or 1 player legally going in motion just before the snap), all 11 must be perfectly still for 1 second.