Entertaiment is any activity that diverts or amuses people in their leisure time. It may be something a person creates themselves, such as solving a crossword puzzle or playing a game; or it may be something they consume, such as watching a movie or listening to music.
Some brainwave entrainment frequencies are known to enhance certain cognitive processes such as gamma brainwaves which enhance alertness and intuition. However, it is important to note that the entrainment stimulus needs to be at just the right strength in order to work.
The optimum zeitgeber for this purpose is a light or sound wave at the speed of a natural rhythm, such as a heartbeat.