I'm certain you mean cloaking and it will very bad for your site. Basically its getting links that are hidden usually by using a link color that is identical to the background color so that the links aren't easily identified by human visitors
Showing the users one thing and search engines something different. Text contianing keywords and phrases hidden behind an image would be a form of cloaking. There are a lot of different ways webmasters cloak and it's considered a black hat tactic that can get your website penalized or even banned.
Cloaking describes the technique of serving a different page to a search engine spider than what a human visitor sees. This technique is abused by spammers for keyword stuffing. Cloaking is a violation of the Terms Of Service of most search engines and might results in a ban.