It is also called organic referencing.
The objective of a SEO expert is to improve the visibility of the websites he supports by making them gain places on search engines (Google, but also Yahoo !, Bing, etc.).
SEO defines techniques used to improve the position of a website on the search engine results pages.
The goal is to bring together Internet users interested in products / services or informative content. We say that a site is well optimized or referenced if it is in the first position of a search engine on the desired queries.
Steve Umuhire