The top node is the initial, the very top of, or starting point of a tree data structure. It is the only node which has no parent.

Top Node of a Tree Data Structure

A tree data structure is accessed beginning at the top node. Each following node is either a single leaf on the tree structure or has one or more child nodes and is called the parent of those nodes. Unlike a real tree, the top node is always shown at the top of the structure, and the leaves are shown at the bottom.

Home Page

The home page is the top node of any website. Every website should have the home page url defined only one way. Furthermore, do not allow your html sitemap to become an alternate top node by indexing it the in search engines.