Entertaiment is a broad term that refers to any agreeable occupation for the mind, diversion, or amusement. It is the source of pleasure, gratification, and enjoyment: solving the daily crossword puzzle is an entertainment for many. It can be an activity for one person, or a performance intended for a group of people, or a spectacle broadcast to a global audience. It can even evolve from an activity used in hunting or war into a spectator sport, such as fencing or archery.
You may occasionally see this abbreviated to entmt on a flier or in industry news publications where space is at a premium. But it is rare to use it in general prose.