Black Hat SEO is when a method and strategy targeted at directly improving the search engine rank of your content is used with no regard for how good the overall user experience is when the content is viewed.
Black Hat SEO methods will yield fast results as they often exploit a way that the search engine determines where web pages rank, but this is normally at the expense of overall quality.
Search engines constantly improve the way they rank content and leave behind the flawed methods that Black Hat SEO employs. This results in a very short life-span of a page or website being highly-ranked by the use of Black Hat SEO methods.
