The word Entertaiment can be explained in many ways. It is an activity understood objectively, it encompasses communication between text and audience, it offers pleasure and requires an audience to exist and occurs in a passive form.
It hits the points the brain was evolved to react deeply on such as backstabbing, murders and other themes in a social world. Entertainment can also stimulate the brain to release seratonin and dopamine.
It is something that can be adapted to any scale, from an individual choosing a pre-recorded entertainment from the immense array available to them; through a banquet suited to two; or a performance aimed at thousands of people.