Let me start of by saying that although I am not an SEO engineer or specialist per se, I very much fall into the camp of utilizing White-Hat SEO techniques. I don’t engage nor do I recommend anyone get involved with anyone that partakes in Black-hat SEO techniques.
So what are examples of Black-Hat SEO techniques? I will do my best to give simple explanations.
1. Using Invisible Text: Anyone that uses invisible text such as using a white-colored font on a white background, a black-colored font on a black background, or any similar colors for both the text and background is using the “invisible text” black-hat SEO technique. They are trying to hide irrelevant content from the user which search engine spiders may pick up.
2. Doorway Pages: A doorway page is a “fake” page designed specially for search engine spiders to pickup on but users never get to see or read. Doorway pages tend to be very spammy and loaded with keywords that would be non-sensical to the average reader.
3. Keyword Stuffing: This technique is self-explanatory. This is when web pages are stuffed with keywords to the point where the content is nearly unreadable and nonsensical.
4. Link Farms: This is the case where hundreds of websites are created through automation for the sole purpose of producing illegitimate back links. There is nothing wrong with creating multiple websites that point to each other. However, it becomes obvious when the number of websites run extremely high and the purpose of each website is not clearly defined.
There are other more obscure black-hat techniques that get very technical in nature. But the one thing they have in common is that the use of those techniques is done secretly and if found out, they can get you banned from a search engine.