if you are talking about football then yes. if any side crosses the line of scrimmage before the quarterback says hike than it is offsides
it is defense
if your on offense it's false start, if your on the defense it's offsides
offense wins battles, defense wins games
if you have the ball in your possession then your on offense if not your on defense
In American football there are 11 players on defense as well as offense.
Offense and Defense
Offsides is if the defensive player jumps across the line of scrimmage while the ball is snapped. False start is when an offensive lineman jumps or moves his hand after he gets set. Offsides = Defense False Start = Offense
A defense is the opposite of offense they stop the offense from touchdowns,passes and etc. If the offense fumbles the football they got a ready to recover it. They can also catch a ball called a intercepation.
If the offense team misses or failed to gain 10 yards, the defense will take over the ball thus changing the defense to be on offense and offense to be on defense.