Cloaking is the presentation of alternative pages

Cloaking is the presentation of alternative pages to a search engine Spider so that it will record different content for a URL than what a human browser would contemplate. Cloaking is typically done to effect a higher search engine position or to artifice users into visiting a site. In such cases cloaking is considered to be Black Hat SEO and the offending URL could be Blacklisted. However, cloaking is sometimes used to save personalized content based on a browser's IP address and/or user-agent HTTP header. Such cloaking should only be practiced with a search engine's knowledge or it could be construed as black cap cloaking.