How many players does each team have on the field at one time in the NFL?

How many points is a field goal worth? How many points is a safety worth? How many points is a successful kick after a touchdown worth? How many points is a successful two-point conversion worth? How long is an NFL playing field between the goal lines? How deep is each end zone on an NFL field? How many downs does an offense get to advance the ball 10 yards? How long is each quarter in an NFL game?