Search Engine Optimisation (SEO) is a term used to describe strategies and techniques for improving the organic (non-paid) search engine rankings of a website.
Done ethically, search engine optimisation involves:
Search engine optimisation does not involve meta keyword tags, keyword 'stuffing', random reciprocal links, doorway pages, hidden text, writing hundreds of articles about nothing, or the myriad other techniques that many people still try to use to improve search engine rankings.