Search Engine Optimisation (SEO) helps to improve the presence of a website or webpage on the net by making it more visible. Three characteristics of a website can be tweaked and tuned to help this process. The layout of the site, the content and in particular the language used can be setup to make the site more prominently listed by search engine results pages (SERPS).
Search engines, for example google or yahoo, use indexing based on keywords and/or search terms. A ranking system is then applied to determine where sites should appear on a results listing. Clearly having private and in some cases highly secretive organisations with the power to alter who appears where on a listing should be of concern to any critically minded individual.
Organic SEO is the term applied to changes made on the website itself, this is called onsite SEO. Using other ways of promoting a website, via social media for example, is called off site SEO. Organic SEO does not include paying for increased traffic to the site. When using third party promotion tools and paying for them, such as Adworks, the term applied is search engine marketing (SEM). Ultimately with both SEO and SEM the use of language is of central importance.