Black Hat SEO encompasses optimization methods that violate spam policies and are designed to deliberately manipulate search engines in favor of a website in order to cheat the system into granting better rankings rather than earning them.
The term is an umbrella term for a whole range of techniques, including:
Link spam: artificially building ranking signals through purchased, exchanged, or otherwise manipulatively generated backlinks
Hidden text: content deliberately hidden from human users so that search engines can capture additional keywords or information
Keyword stuffing: the unnatural accumulation and repetition of search terms
Cloaking: displaying different content to users and crawlers with the aim of manipulating search engines
Scaled Content Abuse: the mass production or compilation of content with no real added value in order to manipulate rankings
In contrast to the “black hat” is the hero: White Hat SEO, optimization within the rules that focuses on real added value.
Black Hat SEO can certainly work, but it risks penalties or, in the worst case, exclusion from search results—not to mention a potential loss of trust among users.