It is common practice for Internet users to not click through pages
and pages of search results,
so where a site ranks in a search is
essential for directing more traffic
toward the site.
The higher a website naturally ranks in organic results of a search, the greater the chance that that site will be visited by a user.
SEO is
typically
a set of "white hat"
best practices
that webmasters and Web content producers follow to help them achieve a better ranking in search engine results. Search Engine Land's Guide To SEO explains the ranking factors in more depth, in a tutorial providing tips and advice on implementing them.
See Five tips for Driving Search Engine Traffic and How Do Web Search Engines Work.