I try to follow american football as much as I can, but having lived my whole life in Europe it's not something you get exposed to alot. So I had to decipher the game by myself.
One particular rule that I have always had hard times figuring out is the interference. So what I know is that when the QB throws a high/deep ball to a WR the defender who's running with the WR cannot interfere with the receiver until some arbitrary point.
Seeing as the sport is a physical, contact-based one how do you defense if you can't really tackle a player going for a touchdown or a major 1st? Could someone explain this rule in plain English (i.e. please no c/p from a rulebook)?