Pillar Page
noun

Definition:
A comprehensive, authoritative page that broadly covers a core topic and links out to more specific related subtopics (cluster content). Pillar pages serve as the foundation of a topic cluster strategy to build topical authority and improve internal linking.

Usage:
“They created a pillar page for ‘digital marketing’ that linked to subpages on SEO, PPC, and email marketing.”

Compare:
topic cluster, cornerstone content, internal linking