Binary trees

A tree is composed of three parts: a root, children and leaves.
From the ground to the sky, the first part of a tree is the roots, then comes the trunk (no name for it in a binary tree), then it spreads out into branches (or children), and finally the leaves

This is an example of a tree where the leaves are digits and the children and root are mathematical symbols

(3 + (5 - 2))* 9