Black hat SEO refers to the use of aggressive SEO strategies, techniques, and tactics that focus only on search engines and not a human audience, and usually do not obey search engines guidelines.
Black hat SEO is more frequently used by those who are looking for a quick financial return on their Web site, rather than a long-term investment on their Web site. Black hat SEO can possibly result in your Web site being banned from a search engine, however since the focus is usually on quick high return business models
Some examples of black hat SEO techniques include keyword stuffing, invisible text, doorway pages, adding unrelated keywords to the page content or page swapping (changing the webpage entirely after it has been ranked by search engines).