What is a leaf node?

A leaf node in a tree data structure is a node that has no children. It is the end point of a branch in the tree, and it does not have any sub-trees beneath it. Leaf nodes are also known as terminal nodes or external nodes. In a binary tree, a leaf node would have a maximum of two children. Leaf nodes are often used in tree traversal algorithms, as they signify the end of a branch and allow for easier traversing of the tree structure. In terms of application, leaf nodes are also used in decision-making processes, such as in machine learning algorithms, where they represent the outcome or prediction of a model.