Black Hat SEO is the use of various tricks in order to increase your website ranking in search results. Such tricks may include spamming other websites with links, putting enormous amount of key words in the keyword tags, using invisible text on web pages, using a fake page that is not seen by the visitor but for search engine spider bots only and more.
As a whole these are techniques that are used to get higher search rankings in an unethical manner.
Such techniques may have been useful in the past. Nowadays, you will be severely penalized by search engines if you try to use such tricks in order to improve your website search results ranking. By any means it is not advisable to employ Black Hat SEO techniques as this will not lead to improving your web site ranking. On the contrary – it will eventually result in lowering its ranking.