There is a pilot and a co-pilot. At any given time in a flight, one will be the "pilot flying" and the other will be the "pilot monitoring." That is exactly the

There is a pilot and a co-pilot. At any given time in a flight, one will be the "pilot flying" and the other will be the "pilot monitoring." That is exactly the point of the quote: there are two in the cockpit, and one should always be checking what the other is doing.