The practice of showing one version of a web page to search engine spiders & a different version to end users.
Cloaking is a Black Hat SEO technique as it makes search engines rank the page on the basis of content that doesn’t really exist. It provides users with results they didn’t expect. The version shown to users might not even be relevant or helpful to their search query.
For example, a web page appears to contain all relevant keywords when a search engine views it but when a users opens it, there are no keywords.
Unapproved cloaking is against search engine guidelines & can result in websites being penalised or banned from the search engine’s index.
Approved cloaking typically only happens with certain search engines that offer a paid inclusion program. As part of this program, websites pay a fee to search engines in order to appear in the results.