It's a strange question.
Even if you could explain who and what you are, would it answer the question?
Each experience building, forming, shaping...making us who we are.
My response is simple and a let down for most.
"I am this way because of the choices I have made."
For 99% there is the immediate rebuttal, "Yeah, but what exactly. And what about your childhood...and what about...and what about...."
Silence.