Python

Like if you are looking for a file withing a deeply nested folder structure... You would implement recursion, so on each step, it would go one level down, until it finds the file you need

So in what case should a recursion stops when traversing through a tree?

That comes with built-in structure.

I hardly suggest you to not use videos. Videos make you follow steps you may not understand, and once you get stuck, they proceed without you understanding. So you have to spend double of the time looking up for a solution online etc while books are more explainatory and guide you, making you understand each single word.