This section is about Search Engines Optimization.
The ideal situation is for your website to come up first in a search using Keywords or Key-Phrases in the major search engines in Google, Yahoo, Excite, Lycos, AltaVista, Infoseek, ...etc. Actually anywhere in the top ten or twenty positions of a search is outstanding.
Search engines read your page and store words on the page that are referenced when someone does a search. If the word used for the search isn't on your page there will be no match and your page will not be listed. However... each search engine uses a different technique for locating words on your page. Some search engines look for keywords or "metadata" that are actually in the HTML code and are not visible to the person viewing the page. The also scan the content or text to see keywords and also relevance to the page, website, business, product or service.
Most engines use a relevance factor (page rank). Sometimes they display this as a percentage or points. For some... the relevance is determined... not only by how many times the words used in the search are in a page... but also how close they are together.
Please check out the SEO Opinion page for an honest evaluation of the state of the art in SEO.