With respect to the Fad which is no longer a Fad and is here to stay, What exactly is MMA?

Now we see MMA schools popping up all over ther place, with students flocking to train there. But what does it consist of. what makes a valid MMA school.

If an Instructor did say TaeKwonDo and did a bit of J-JJ or B-JJ does this make him qualified to teach MMA, is it just not TKD with a bit of JJ thrown into the mix

Or is it a Muay Thai Teacher and BJJ Blackbelt that allows someone to "create" an MMA school

I can't work out WHAT the differences are to justify it being MMA and not just X-style with extra stuff added.
A man is but the product of his thoughts what he thinks, he becomes.