What does a computer’s hard disk have in common with a tall oak? While it may not look like a tree on the outside, the hard disk is organized the same way. Directories of files and folders on a hard drive are organized into branches, where each directory is a branch with files and folders. Folders make up the branches, while files are the leaves. Therefore a leaf is a file within a directory on your hard drive.
Technically speaking, a leaf is a node on a tree with no child nodes. Because files cannot have child nodes like folders can, they are always leafs. When referring to a tree structure, a leaf can also be called a leaf node.