Okay kiddo, do you know what a tree is? It's kind of like a family tree, but instead of people, it's a way to organize information. A red-black tree is a special kind of tree that has some rules.
Now, imagine you have a tree with a bunch of different colors on it. Some are red and some are black. Each color means something different. Red means that it's a new node, and black means it's an old node that's been around for a while.
Left-leaning means that the tree leans to the left when you look at it. It's like if you have a stack of books and the top one is smaller than the one under it, and so on. The left side of the tree is the smaller side.
So, a left-leaning red-black tree is a special kind of tree that has red and black nodes, and it leans to the left. It's like a fancy way to organize information, kind of like a family tree, but for computer programs.