Cloaking (page cloaking)

It’s a practice of taking a webpage and building it in a way so it displays different content to people and to search engines. That way, at least in theory, you can get good ranking for your desired keywords (by presenting an optimized page to the spiders) and then present real people with unrelated offers and content. While this might work from a marketing standpoint it can also get you penalized or even banned very quickly.