White-hat SEO is a marketing strategy, which helps the site to increase its relevance for Search engines and hence bring more traffic and sale for the business. White-hat SEO considers how that is done, what algorithms work, what key phrases people use and what people who search are looking for. They use that information to arrange their site in such a way that it is optimized for the search engines.

"Black Hat" SEO also called spamdexing will use such methods as link farms, and keyword stuffing, cloaking, doorway pages etc. so that those who use search engines are harmed by the ‘wrong’ presentation the site. Search engines regularly look for sites who use such methods and if they do, they could have penalized them.