Hovering is a term used to describe the act of navigating (or "aiming") a tablet pen across a tablet by holding the pen above the surface of the tablet while still inside of the active hover zone. Thus you are "hovering" the pen above the tablet. This is a method of pen navigation in opposition to dragging. It can be found across players of all skill levels, although it is most often associated with highly skilled players.
Arguments in favour of hovering often claim that it reduces/removes the need to buy replacement nibs, removes the need for a tablet cover, and is (technically) "faster" due to a lack of friction. Whereas arguments against hovering often claim that it is much more difficult to accurately stop or turn on jumps and right angles.