A content cluster (also called a topic cluster or pillar-cluster model) is a content architecture strategy in which a broad “pillar” page covers a core topic comprehensively, and a collection of more specific “cluster” pages explore related subtopics in depth — with each cluster page linking back to the pillar and vice versa. The internal linking structure signals to search engines that the site has deep, interconnected expertise on the subject area. Content clusters emerged as a response to semantic search: rather than targeting individual keywords in isolation, they position a domain as an authoritative source across an entire topic. The pillar page typically ranks for high-volume head terms, while cluster pages capture long-tail queries. Planning a cluster before publishing ensures the internal linking is consistent and deliberate rather than retrofit after the fact.