Search engine optimization (SEO) is a website promotion strategy, the goal of which is to get your site to appear at the top of search engine results under keywords or phrases appropriate to your business. For example, a site that sells CDs online will want to be found in major search engines such as Google, Yahoo, MSN, AltaVista and AOL under key phrases such as "online CDs," "buy CDs," or "CDs for sale."

There are 1000s of factors that influence rankings - SEOers discover those factors impliment strategies to increase their rankings based on those factors.