Black Hat SEO is a type of SEO services that try to trick the search engine and manipulate the ranking of the site. These are often are not complying with the rules of the search engines. It uses keywords not related to have more traffic to the website and others spam to get more popularity of the site. An advantage of this method is that you can easily get at the top of the search engines, but can be risky, because if they discovered the spam, the site will be banned from the list. This also disappoints visitors due to lack of relevance of the keyword they are looking for in the search engines.