as with binary search trees more generally, a wavl tree consists of a collection of nodes, of two types: internal nodes and external nodes. an internal node stores a data item, and is linked to its parent (except for a designated root node that has no parent) and to exactly two children in the tree, the left child and the right child. an external node carries no data, and has a link only to its parent in the tree. these nodes are arranged to form a binary tree, so that for any internal node the parents of the left and right children of are itself. the external nodes form the leaves of the tree. the data items are arranged in the tree in such a way that an inorder traversal of the tree lists the data items in sorted order.