Black hat SEO refers to a set of practices that are used to increase a site or page’s rank in search engines through means that violate the search engine’s terms of service. Black hat SEO is most commonly defined as a disapproved practice that nevertheless could increase a page’s ranking in a search engine result page. These practices are against the search engine’s terms of service and can result in the site being banned from the search engine and affiliate sites.
Actually, black hats are the bad guys. In some industries, black hats are referred to as hackers. Black hat techniques ignore searcher intent and attempt to bypass best practices by cheating the system and gaining search visibility through unscrupulous practices. Although black hat SEO is not illegal, it does violate webmaster guidelines set out by search engines. In other words, it is still against the rules. This means if you engage in black hat SEO, you must be willing to get hit with nasty punishment to pay penalty.
Common examples of black hat SEO include the use of invisible text, doorway pages, keyword shuffling, page swapping, or the addition of unrelated keywords to a page.
But it should not be used because it can lead to search engine rankings or even cause a site to disappear from search results entirely. Because the black hat SEO technique goes explicitly against search engine terms of service, search engines may penalize and even ban sites from appearing on their search results pages if they engage in these tactics.