Play serves a variety of biological functions, and of course, it isn't just humans who like to do it. You probably only need to own a pet to know that.
Play is important for forming social skills. It's literally practice at being a member of a group, and at knowing your place. People, like animals spend a lot of time role-playing and play-fighting (practice at how to do a social role, and jostling for social position, as in privileges and status).
Play is good for locomotor skills. It is an enjoyable way to develop valuable gross and fine motor skills.
Play's other primary function is to make learning enjoyable. As humans, one of our most developed skills is in how good we are at learning. Not just at learning, but at teaching, and at learning how to do things better than we have done them before. To capitalise on this skill we have to enjoy learning in itself.
Play is important for forming social skills. It's literally practice at being a member of a group, and at knowing your place. People, like animals spend a lot of time role-playing and play-fighting (practice at how to do a social role, and jostling for social position, as in privileges and status).
Play is good for locomotor skills. It is an enjoyable way to develop valuable gross and fine motor skills.
Play's other primary function is to make learning enjoyable. As humans, one of our most developed skills is in how good we are at learning. Not just at learning, but at teaching, and at learning how to do things better than we have done them before. To capitalise on this skill we have to enjoy learning in itself.