Keyword relevance depends heavily on on‐page factors. In addition to the raw text or body of the page, search engines use a number of criteria to understand what the page is about:
the title of the page: does the keyword appear in the title of the page?
the prominence and placement of keywords on the page: is the keyword em‐phasized on the page – by being used in headings, bold text, italicized text, link text, bulleted lists or larger text?
the meta description of the page: does the ‘description’ meta tag in the page’s markup contain the keywords?
keyword density: does the keyword appear a number of times?
anchor text (link text): do inbound links to the page contain the keyword?
A page where “used books” appears once or twice in the body of the page will be considered less relevant than a page where it appears in content headings, which will be less relevant than a page titled “used books” which also uses it in the meta description and main body of the page