So in the NFL if a player goes out of bounds on a play he must "re-establish position" inbounds before he can touch the ball. How or what does re-establishing position entail?
From the 2019 NFL Rulebook Rule 3.21.2
Article 2. Player Inbounds
A player who has been out of bounds re-establishes himself as an inbounds player when both feet, or any part of his body other than his hands, touch the ground within the boundary lines, provided that no part of his body is touching a boundary line or anything other than a player, an official, or a pylon on or outside a boundary line.