Aft means in or toward the back of a boat or an aircraft. On a ship, that is toward the stern — the back end. On a plane, that is toward the tail. Crew say “move aft” or “the aft cabin”. It is sea and air talk; you do not say a room in a house is aft. It can tell you direction (go aft) or describe a thing (the aft seats). The front of the ship or plane is fore or forward. Though actually, aft is a close family member of after, and both go back to an old word for “behind”, but you cannot swap them in a sentence. After is usually about time (“after lunch”). Aft is about place on the vessel. If you say “after the plane”, people will hear time, not the tail.