A catch seems like one of the simplest things in the game of football, but to this day, it's hard for anyone to define. The NFL has rules that dictate a player must have two feet in bounds and make a football move while having complete control of the football.
The problem is that people have trouble defining certain aspects of those rules.
Slow-motion and high-definition replays allow officials to break down every questionable catch frame by frame, so they can see things the naked eye cannot, which results in several overturned calls on would-be receptions.