Cloaking is creating two pages of the same original. One for the user and one for the search engines. Users see a page optimized for the user and search engines see one optimized for them. This again can sound the death knell for the site.
The page the search engine robots see is cloaked because it is invisible to the visitor.
This is not something many people will implement. Only those webmasters who have advanced knowledge will attempt to do cloaking. However you need to understand this can be disastrous from a search engine optimization / ranking point of view.
The idea behind cloaking is to optimize one page heavily for search engines going the extra mile including additional text etc, stuffing keywords often senselessly, which will be irritating and meaningless for the site visitor.
Never resort to cloaking. If you are not developing your site make sure those who are developing it for you do not employ such tactics.
Next: Hidden Text
Quotable Quotes:
“Advice tells you much about the person giving it.”