More and more, companies are becoming aware of the crucial importance of SEO (Search Engine Optimization) which can be defined as the process of improving the visibility of a website on search engines via « natural » search results in contrary to Search Engine Marketing (SEM). The purpose of this article is to give a quick overview of the SEO process. Indeed, the fact is that SEO can be divided into three main logical steps: web audit, on-site and off-site SEO.