What is a Blackhat Niche?

Hi,

I am new here. I was searching on Google about what is a blackhat niche. Most answers are all about SEO. It is tough to find specific answer about a 'blackhat niche'. What is it?

Plus, if I find some glitch in the software or find some clever method in a game, turn it into an ebook, and do content locking on it, will it be a 'blackhat niche'?

I am confused. I am sorry if it is a stupid question.