Organic SEO (search engine optimization), sometimes referred to as natural search optimization, website SEO, or just plain old SEO, is the process of improving the rankings of a website in search engine results for specific targeted keyword phrases. Organic search results are "free" in a sense – that is, you don’t pay for a listing in the search results pages for your keywords, as you do with pay per click advertising, like Google’s AdWords and others.
Unlike paid search, the benefits of organic SEO can be seen long after the initial SEO work has been completed. With paid search, your ads in the search engine listings stop once you stop paying for them or you have met your budget. Organic SEO techniques, on the other hand, can keep showing up for an indefinite time period. Of course, it helps to continue your website SEO efforts at least on a limited basis to help maintain your rankings and improve those where you’re not ranking as well in the search engines as you’d like.