Entertaiment is the activity of evoking strong emotional reactions. It can include everything from a comedy show to reading a book of murder mysteries. It often hits on points that the brain was evolved to deeply react to, like social backstabbing and murders. Entertaiment also includes things that evoke thought, such as documentaries and puzzles. It can be enjoyed by one person or shared with others, as in a sport or a multiplayer video game.
Different people will prefer different forms of entertainment, depending on their mood or the kind of experience they are looking for. These might vary from cartoons to a jazz concert to an elaborate drama.