In Football, a completion is when a receiver, usually a wide receiver, running back, or tight end successfully catches a pass. For a completion to be recorded, the receiver must catch the pass, land in-bounds, and maintain possession of the football for long enough to be considered a ball carrier. If a receiver fails to do any of those things, the pass is called incomplete.
If the ball touches the ground after the pass before a player gains possession of the ball, it is also called an incomplete pass. If a player completes the catch and becomes a ball carrier, then is tackled, the player is ruled down and the next down in the down cycle begins. If a player is tackled while in the process of catching the ball and the ball is not caught, it is called an incomplete pass. Any incomplete pass stops the clock if there is two minutes remaining in either half.
If the football quarterback throws the ball to an area where there is no receiver, a penalty called intentional grounding is called. The quarterback must be in the pocket when the ball is thrown. Any throw that is launched without any logical chance of it being thrown is known as intentional grounding.