Adding point of interest
Waypoints and Target points have in common that they are permanently displayed on the map. What makes the difference is their concept: Waypoint is always created from current GPS position and is intended to serve as a note you leave for a place that impresses you in some way (hopefully positive).
Target point, on the other hand, is a point of certain importance, for instance the place you are staying in.
Map zone is a rectangle you select on the map and eventually you may for example cache map sources for it. This is a handy feature if you intend to go to the mountains where is poor signal and so you cannot rely on the immediate Internet connection.