1) Cloaking:
This is a black hat technique that is on deception. It is an optimization practice where you present a content to search engine and presents a different one to the users. The sole objective of this method is to help their content rank for various keywords that are not relevant to the content they present.
No one likes deception; Google is not an exception. Search engines are known for crawling and ranking websites often. They do this often with multiple IP addresses. As such, You can be sure that any website based on cloaked content will not go far.
2) Poor Content:
Offering poor content that is of no value to the user is a common back hat technique. This class of content also include copying content from another website. Since Google Panda update came on board, they have started addressing the issue of copied content. Now Google is good at fishing out copied poor content.
Still, on poor contents, some marketers add invisible keywords to help their content rank for this set of keywords. It is another deception; the content will appear for the keyword even when there is no related content. It leads to user dissatisfaction, but quality and original content leads to user satisfaction and repeated visits.
3) Duplicate Content
It is another form of black hat technique that Google frowns at. Duplicate content refers to content that is found on the internet in more than 1 location. Each content is expected to appear in just on URL, but when search engines find an exact match of content in more than one location.
The issue here is search engine been able to place which is much more relevant amidst the content. Search engines are known to love unique and genuine content. They perceive duplicated content as a sign of manipulation in other for marketers to gain ranking
To indicate the original version of your content, you must implement the canonical tag.
4) Invisible text
It refers to text that is visible to search engines but invisible to human eyes. Black hat marketers use this as a measure to include irrelevant keywords. They do this to increase the probability of the content showing up for more search terms.
In the old days, Cloaking was called Bait and Switch, while the copied content you describe as one type of Poor Content was called Plagiarism.
I've always been disgusted when people do these things, and am glad to know these create a loss in the long run for the Cheaters.
Much appreciation for your articles!