Google’s Gary Illyes discusses the benefits of a hierarchical site structure for SEO and the appropriateness of a flat site structure for simple websites.

Flat Site Structure

A flat site structure, where every page has a home page link, was used in SEO strategy to distribute PageRank, allowing each page maximum ranking. However, Google later reduced PageRank’s influence, removing the need for a flat structure.

Hierarchical Site Structure

Hierarchy organizes content by order of general to increasingly specific topics. In a hierarchical website structure, the home page represents the site’s general topic, followed by categories and subcategories, each containing articles related to the same topic.