Experience and levels

What doe the levels and experience represent? I can’t find any information on them.

I understand they reflect general progress, but are there any milestones or just a arbitrary method of showing progress?

How many levels are there?

The reason I am asking is I am considering tying a reward for my child to the level progression and would like to better understand how they function.

Apologies for the delayed response. Have you looked at the parent guide? I’ve added a link here.