The Try (Law 8.1)

A try is scored when an attacking player is first to ground the ball in the opponents' in-goal area (on or beyond the goal line, short of the dead-ball line and touch-in-goal lines). Grounding the ball requires downward pressure with the hand, arm, or upper body (chest and front of the shoulder).

Source: Law 8.3

Send this to your friend — argument over.