Search Engine Optimization is the process of optimizing a website so that it receives more traffic from search engines. The ultimate goal of anyone using SEO on their website is to get their site listed on the first page of any search engine.
Not having any SEO work done on you website is akin to having a physical store with no store sign or advertising. In this example it is evident that very few or no people at all will visit the store. The gist of this is that if none of the search engines can find you, then you will get zero traffic coming to your website.
SEO is important because search engine results are powered by “Spiders” that crawl the net looking for websites and the information they hold. Spiders look only at text and not at the graphics. So you are ranked purely on content and not how good your website looks. This is why people who are interested in getting their website into the top rankings don’t bother with Flash or any other type of heavy graphics. These add a nice visual element, but have no value towards any SEO.
The whole point of doing SEO is to get on the map. As you go along and refine your keywords, you will want to appear higher and higher in searches. Being ranked number one for a certain keyword is what you should work at. This highlights the fact that SEO is an ongoing process which requires constant attention. The only instance where low SEO is required is when it comes to industries where rare keywords are being used.