The actual energy/mass that shot out from the big bang event. We don't know the actual formation of that stuff but maybe it has always existed in some form until it all collected into one point with the entire mass of the universe existing in a small point. The mass flowered into the universe in a "big bang" a quaint term for the sheer amount of power released into, everywhere all at once.

Quantum Fields can just exist on their own and create interesting interactions. Look them up if you want, really neat stuff. It's an interesting phenomena that can create energy by itself I think.