Search engine optimization is the process of manipulating potential online clients to lean toward a specified marketer by creating some new content, but mostly by linking, tagging, and so on existing content so that a user will notice said content. In other words, when a user types in the word "auction" into Google, eBay may pop up thanks to how much content is out there regarding auctions, but more importantly connecting, eBay with the tag "auction." If SEO did not do its job, search engines would be useless and ineffective.