Entertaiment is the act of entertaining; something affording pleasure, diversion, or amusement: A crossword puzzle provides entertainment for many.
Entertainment is one of the most powerful forms of human art because it often hits on the points that the brain was evolved to deeply react to, in order to function as a social creature. For instance, stories about backstabbing and murder, which were a very important part of the social world in order to understand the spritual and physical environment of early humans, still provide entertainment today.
Entertainment is also flexible enough to be adapted to almost any scale: from personal activities, such as solving a crossword puzzle, to banquets adapted for two people, to performances aimed at thousands or even the entire global audience.