Entertaiment is anything that stimulates the brain to realease seratonin and dopamine, wich is good for us considering we are shaped to understand the world we live in. It often hits the points we were evolved to react deeply to like murders, backstabbing and other themes in a social context that was vital for survival.
It can be any form of leisure activity that is consumed. Bates and Ferri (2010) define entertainment as an objectively understood activity that encompasses communication between text and audience from external stimulus, offers pleasure, requires an audience to exist and occurs in a passive form.
