what does the term search engine optimization means

what does the term search engine optimization exactly means. how are the searh engine optimized. is search engine optimization important for displaying the names of the sites

SEO seeks to increase a site’s visibility in search engines and enhance its value to visitors through topical page design, consistent HTML tagging, and focusing content on core keywords.

I really thank you for that information Nick, I was wondering the same thing and now it is all cleared up!