If I want to explain recursion to a ten years old, I will not explain to him mathematicali but I will take a piece of paper and fold it in half, then ‘recurse’ by folding the already-folded sheet in half again, then again and again until it’s so thick that I can’t fold it anymore. This is the base case, where the recursion stops. I know it’s a shitty explanation but it’s all I could really come up with off the top of my head.