it's when girl shows her tits 2 boy.

It also doesn't just mean what a person does to have fun, but it can also mean to amuse someone with something. For example, "I want you to entertain me". Meaning - "I want you to keep me interested, amused, etc."

Are you asking for the meaning of the word 'entertainment'? Entertainment is anything that a person does to have fun. Example: watching a movie with friends is a form of entertainment.