What is the difference between encroachment and off sides in football?

Answer 1

Encroachment is when a defensive player crosses the line of scrimmage and touches an offensive player; play is blown dead, 5 yard penalty. The NFL has changed the rule to include crossing the line and causing an offensive player to move. Offsides is when a defensive player sets up or crosses over the line of scrimmage before the snap, and doesn't get back in time; the play is blown dead if unabated to the QB, otherwise it's play-on and a 5 yard penalty if the offense accepts. There is technically no such thing as "offsides" on the offense. A false start is when the offense jumps before the snap; 5 yard penalty.