Explain Def Poetry Jam to me

I think I get it, I really do. However, there is something gnawing on the edge of my mind telling me, “no, you don’t get it.”

It seems to be about performance, variety of rhythm and internal rhyme. It also seems to be about anger, disappointment, and hope.

It isn’t about being subtle, it seems to be about being creatively obvious – which is strange to my mind and experience. And what’s with the singing interludes?
Anyone got something out there for me?