Which player holds the NFL record for most career receiving yards?

What is a "flea flicker"? What is it called when the ball carrier loses possession of the ball? Which player holds the NFL record for most career passing yards? Which player holds the NFL record for most career rushing yards? Which player holds the NFL record for most career touchdowns? Which running back set the NFL single-season rushing record with 2,105 yards in 1984? Which quarterback set the single-season records with 5,477 passing yards and 55 touchdown passes in 2013? Which running back became the first to rush for 2,000 yards in a season, in 1973?