Search engine optimization (SEO) is the process of developing a marketing/technical plan to improve visibility within one or more search engines. Typically, this consists of two elements.
On a technical side, SEO refers to ensuring that a website can be indexed properly by the major search engines and includes the use of the proper keywords, content, code, and links.
On the marketing side, SEO refers to the process of targeting specific keywords where the site should “win” in searches. This can be done by modifying a website to score well in the algorithms search engines use to determine rank, or by purchasing placement with individual keywords. Often, SEO programs are a blend of several elements and strategies. 
Note: When SEO is used to describe an individual, it stands for search engine optimizer.
- ^ American Marketing Association, AMA Dictionary.
- ^ SEMPO. Glossary of Terms.