|IMPORTANT: The pass will be ruled complete as long as the two feet touched down inbounds. A receiver must also maintain control of the ball when falling to the ground. A receiver's body can technically be out of bounds and over the plane of out of bounds, but as long as the feet are inbounds it still counts.|
A complete pass is one that was caught in bounds by a player. If a ball is caught out of bounds it is called incomplete because the play stops and was never completed. However, it still is permitted for a player can catch the ball in bounds on two feet and then step out of bounds. The person must also be in control of the ball when making a complete pass in order for it to pass.
If you want to learn more about passes and the boundary lines on the field, check out these tutorials: