Hiding in Hip Hop, who exactly are these Down Low Rappers?

[LGX]

I was reading Terrence Dean's Hiding in Hip Hop autobiography of sorts and was really bothered by one thing: he NEVER mentions who exactly the people are and it agitates the crap out of me. He brags with who he slept with, but this book is starting to feel like a novel. Does anybody have any idea who is down low?