Black Hat SEO

There is no generally accepted definition for black hat SEO. Because, they are tactics which are not considered to be good or fair.

Black Hat SEO is a dangerous method adopted by some of the webmasters to cheat Search Engines such as Google and others but once found by them, then their website is kicked out of their database
They are the one who attempts to improve rankings in ways that are disapproved of by the search engines, or involve deception.

Black hat SEO basically is a short-sighted solution to a long-term problem, which is creating a Web site that provides both a great user experience and all that goes with that. They exploit weaknesses in the algo by breaking the webmaster guidelines. They are primarily about “cheating” / “manipulating” search engines. They are only focused on machine. And of course they are mostly focuses on earning “money without even trying to provide any value to the visitors.
One black hat technique uses text that is hidden, either as text colored similar to the background, in an invisible div, or positioned off screen.

Black hat SEO refers to aggressive practices that “manipulate” search engine and disregard human audiences. Most black hat practices violate rules set by search engines. They are the one who makes spamming.