Originally Posted by Top_Gunn

OK, that analogy works, sort of. Suppose you have a boat that does 10 knots, and you want to cross a north-south stream moving south at ten knots. You are on the west side. River is 10 miles wide (simplifies math).

If you point the bow east and go straight, the current will carry you ten nautical miles south by the time you get to the other side. so you start out and use your rudder to turn the boat so its heading is 045 degrees. Then you neutralize the rudder, go straight on that heading, and you'll end up due east of where you started. The boat will go due east (with the bow pointed northeast).

Just like flying a plane in a crosswind, except that most planes turn by banking.