But above and beyond simple playfulness, all play is more profoundly meaningful than we usually think. Like lion cubs wrestling each other, play is a way to try on adult roles and skills. Human children roughhouse, and they play house. As children discover the world, and discover what they are able to do in the world, they develop confidence and mastery. Play is also a way to be close, and even more importantly, a way to reconnect after closeness has been severed.
Chimpanzees like to tickle each others palms, especially after they have had a fight.
The third purpose of play for children, and perhaps the one that is most uniquely human, is to recover from emotional distresses. Imagine your child has had a hard day at school. They come home and one way or another they show you that they're hurting. They talk about it, or they are irritable and obnoxious. They lock themselves in their room, or they insist on extra attention.