According to webopedia:
SEO is short for search engine optimization or search engine optimizer.
Search engine optimization is a methodology of strategies, techniques and tactics used to increase the amount of visitors to a website by obtaining a high-ranking placement in the search results page of a search engine (SERP) — including Google, Bing, Yahoo and other search engines.
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.
So… it is very important that your website is properly optimized for the search engines. There are many approaches to this task and the rules keep changing. Why? Well… because there are people out there constantly trying to fool the search engines!
I will write more on this topic and how you may educate yourself in a future post.