Search engine optimization 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 consultants that carry out optimization projects on behalf of clients' sites. SEO, or "white hat SEO", is distinguished from "black hat SEO", or spamdexing by methods and objectives. Spamdexing uses a variety of deceptive techniques in an attempt to manipulate search engine rankings, whereas legitimate SEO focuses on building better sites, and using honest methods of promotion. What constitutes an honest, or ethical, method is an issue that has been the subject of numerous debates.

Search engines display different kinds of listings in the search engine results pages (SERPs), including: pay-per-click advertisements, paid inclusion listings, and organic search results. SEO is primarily concerned with advancing the goals of a web sites by improving the number and position of its organic search results for a wide variety of relevant keywords. SEO strategies can increase the number of visitors, and the quality of visitors, where quality means visitors who complete the action the site intends (e.g. purchase, sign up, learn something).

For competitive, high-volume search terms, the cost of pay per click advertising can be substantial. Ranking well in the organic search results can provide the same targeted traffic, potentially at a lower cost. Site owners may choose to optimize their sites for organic search, if the cost optimization is less than the cost of advertising.

Not all sites have identical goals for search optimization. Some sites are seeking any and all traffic, and may be optimized to rank highly for common search phrase. A broad search optimization strategy can work for a site that has broad interest, such as a periodical, a directory, or site that displays advertising with a CPM revenue model. In contrast, many businesses try to optimize their sites for large numbers of highly specific keywords that indicate readiness to buy. Overly broad search optimization can hinder marketing strategy by generating a large volume of low-quality inquiries that cost money to handle, yet result in little business. Focusing on desirable traffic generates better quality sales leads, allowing the sales force to close more business.
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Search engine optimization"