Simply having a website will not guarantee success today. People need to be able to find your website via the numerous search engines available. Unless your business is so unique that you have no competition, you will need to ensure that people find your website before they find your competitors. The process of optimizing a website for search engines is continuous. Search Engine Optimization in a lot of ways can be compared to a foot race with competitors constantly overtaking each other during the race. As your website moves up the list, obviously your competitors will move down and vice versa.
PageRank relies on the uniquely democratic nature of the web by using its vast link structure as an indicator of an individual page's value. In essence, Google interprets a link from page A to page B as a vote, by page A, for page B. Google looks at considerably more than the sheer volume of votes, or links a page receives; for example, it also analyzes the page that casts the vote. Votes cast by pages that are themselves "important" weigh more heavily and help to make other pages "important". Using these and other factors, Google provides its views on pages' relative importance.
Of course, important pages mean nothing to you if they don't match your query. So, Google combines PageRank with sophisticated text-matching techniques to find pages that are both important and relevant to your search. Google goes far beyond the number of times a term appears on a page and examines dozens of aspects of the page's content (and the content of the pages linking to it) to determine if it's a good match for your query.
This might be the single most informative article we have ever found on Search Engine Optimization