A set of related pages organized around a shared subject and connected through structured internal links.
A topic cluster is a group of pages that address related parts of a broader subject. The group can include an overview, detailed explanations and relevant service or product pages. Internal links help people move between those resources as their questions become more specific.
The cluster is the collection and its relationships, rather than a single central page. A pillar can introduce the subject, while a hub can help people browse the collection. There is no mandatory number of pages, fixed linking pattern or official cluster score that a site must achieve.
Build the group from distinct reader tasks. Closely related wording does not always justify separate pages. When two proposed articles would answer the same question in essentially the same way, consider one stronger resource instead. Add links because the destination provides a helpful next answer, not simply because every page belongs to the same spreadsheet category.
Takeaway: Use clusters to make related content easier to navigate and maintain. Reuse suitable existing resources and expand only where a useful question remains unanswered.
Example
A bicycle shop organizes maintenance resources around tire care, chain cleaning and brake checks. An overview points readers to the appropriate task, and the tire page links to a separate tube-sizing explanation where needed. Each page solves a different problem rather than repeating a general maintenance introduction.
What to check
Check that important pages can be reached through normal site navigation or contextual links. Review overlapping pages and broken connections periodically. A complete-looking cluster diagram is not evidence that the content satisfies readers.
For more detail, see Google SEO Starter Guide.