Search engine optimization (SEO) is a set of methods aimed at improving the ranking of a website in search engine listings. The term also refers to an industry of SEO consultants who carry out optimization projects on behalf of clients' sites.

Practitioners may use "white hat SEO" (methods generally approved by search engines, such as building content and improving site quality), or "black hat SEO" (tricks such as cloaking and spamdexing). White hatters charge that black hat methods are an attempt to manipulate search rankings unfairly. Black hatters counter that all SEO is an attempt to manipulate rankings, and that the particular methods one uses to rank well are irrelevant.

Truly Professional SEO firms concentrate on attaining top rankings without exposing their clients to risk.

A SEO Company is an online marketing firm that specializes in Search Engine Optimization services.

Google SEO is highly dependant upon quality external links to attain top rankings, while Yahoo SEO is more concerned with onpage factors, and concerned with quantity of links over quality.