What is the Goal Line?
The goal line in football is a line on the field marking the front of each end zone. The ball must break the plane of the goal line for a touchdown or 2 point conversion to count. The goal lines extend from sideline to sideline, so players can make a touchdown at any point on the field, as long as it crosses the goal line. The goal lines and sidelines make up the field of play.
Crossing the Line
For a touchdown on a passing play, the player must cross the line and have both feet touch the end zone. If his feet are in the end zone but the ball is shy of the endzone, the touchdown does not count.
The tricky part of these passing play touchdowns is whether the official declares that the player had control over the ball. If he doesn't think he did, he can take away the touchdown. Only part of the ball has to go over the goal line for the touchdown to be good.