this tag should be use when developing techniques against web crawler or spider web bots
Cloaking is a search engine optimization (SEO) technique in which the content presented to the search engine spider is different from that presented to the user's browser.
this technique also known as stealth, basically consist to deliver one page to a search engine for indexing while serving an entirely different page to everyone else.
When a user is identified as a search engine spider, a server-side script delivers a different version of the web page, one that contains content not present on the visible page, or that is present but not searchable. The purpose of cloaking is sometimes to deceive search engines so they display the page when it would not otherwise be displayed (black hat SEO).