Topical authority is an SEO idea: a site covering one subject in depth, across linked pages, is more likely to be trusted and found for it. Google publishes no score.
A dental clinic has one page called dental implants. A rival has the same page plus 12 supporting pages: cost, recovery, bone grafts, suitability, aftercare, and one for each common worry. When a patient searches any of the 13 topics, the rival's pages answer more of what the patient asked next.
Topical authority is shorthand for being the obvious place to learn about one subject. It is an industry term, not a Google metric: nobody can look up their "authority score" in Search Console, and Google's documentation talks instead about helpful, reliable, people-first content and demonstrated experience. But the idea is sound. Search engines and AI answer engines break a question into sub-questions, and a site that already answers the sub-questions well has more to be cited for.
For a business owner this means depth beats breadth. Ten pages that settle one subject usually do more than fifty thin pages about everything you sell.
A good test: take ten questions a customer asked on the phone this month. If your site answers eight of them, you are building authority. If it answers two, you are building a brochure.
BridgeE builds clusters like this through SEO and content marketing, starting from the questions your buyers already ask.