A leaf node is a term used in data structures, particularly in trees, to describe a node that does not have any children. In a tree structure, nodes are connected in a hierarchical manner, and leaf nodes are found at the bottom level. They represent the endpoints of the tree, where no further branches extend. In the context of computer science, leaf nodes are important for various algorithms, such as those used in binary trees or decision trees. They often hold the final values or outcomes, making them crucial for tasks like data classification or searching within a dataset.