You already know how to use a search engine: Simply type in a keyword, and almost instantly, youâ¤™ll receive pages upon pages of websites where the words you searched for appear. Search engines are able to do this by sorting through millions of webpages it has indexed, and then present you with the ones that match your topic.Which begs the question: How does a search engine determine keyword relevance when itâ¤™s faced with millions of webpages to sort through? It does this by following a set of rules, known in tech speak as algorithm. Exactly how a specific search engineâ¤™s algorithm works are tightly-guarded company secrets. However, all major search engines follow a common pattern in indexing keywords on a webpage.