Entertaiment is a thing that makes people happy and distracts them from their everyday life. It stimulates the brain to realease seratonin and dopamine making the person feel good. Usually entertainment hits on things that the human mind was evolved to react deeply to, such as murders and social backstabbing.
A clown at a birthday party, a Broadway show, a stadium rock concert, or your friends fighting over the last potato chip are all forms of Entertaiment. The word originates from the French entretenir meaning to keep company. It has become associated with hospitality and now means amusement or distraction.