A topic cluster is a set of pages that each answer one specific question about a subject, all linking to and from a central page that covers the subject as a whole. The central page is called a pillar or cornerstone page. The structure works because it concentrates internal links and relevance around one topic, which is how a site comes to rank for the whole of it rather than for scattered phrases.
The shape
One broad page: what wedding fireworks cost, how they work, what to ask a supplier. Around it, a page for each narrower question: quiet fireworks for venues with noise limits, fireworks in wet weather, licensing for a private display. Every narrow page links up to the broad one. The broad one links down to each of them. The narrow pages link sideways where a reader would naturally go next.
The narrow pages are the ones you can rank for first, because their queries are less contested. As they earn traffic and links, the pillar page inherits some of that and starts to rank for the head term.
Cluster, pillar, cornerstone
Different names for the same idea from different eras. Cornerstone content is the older term, popularised by an SEO plugin that lets you mark a page as cornerstone so the plugin nags you to link to it. Pillar page and topic cluster came from content marketing in the late 2010s. All three describe a hub page and its spokes.
Why it works
Google discovers and weighs pages through links, and reads anchor text to understand them. A cluster hands it a tidy map: here is the subject, here are its parts, here is how they relate. It also stops you competing with yourself, because each question has one page rather than three overlapping posts.
It is also how a reader actually explores a subject, which is the better reason to do it.
How to build one on a small site
Write down every question a customer has asked you about the subject. Group them. Each question becomes a page with the answer in the first paragraph. Write the pillar last, when you know what it needs to summarise. Link everything as described above, in the body text, with descriptive anchors. Then track the whole set of keywords together, because the cluster improving as a group is the sign it is working before any single term reaches the top.
Where this shows up in the tracker
Every term in this glossary is something the product actually measures or acts on. Plans start at £29 a month, with rank tracking, AI visibility, the daily AI readiness scan, security and domain health, Search Console, backlinks and audits on every one of them.
Related terms
Topical authority
Topical authority is the industry's name for a pattern everyone in SEO has watched: a site that covers one subject in depth, and earns links for that subject, finds it progressively easier to rank for new pages within it. It is not a score Google publishes, and for ordinary web search it is not a system Google has named. It is a useful description of how several real signals add up.
Internal linking
Internal linking is linking from one page on your website to another. It is how Google discovers most of your pages, how it works out which ones you consider important, and how it learns what each page is about from the words used to link to it. It is also the one ranking lever that costs nothing and that you control completely.
Long-tail keyword
A long-tail keyword is a specific search phrase with a small number of searches a month, as opposed to a broad head term with many. Fireworks is a head term; quiet fireworks for a wedding in October is long tail. Long-tail phrases are less contested, so a small site can rank for them, and they are usually typed by someone closer to buying.
Cannibalisation
Cannibalisation is when two or more of your own pages compete for the same search, so Google keeps swapping which one it shows. Both pages are weaker than one good page would be.