A vacuum, Not yet decayed to its ground state. Random quantum fluctuation. Tunneled from nothing to a false vacuum.
A region of space. Containing no matter, nor radiation. Not quite nothing. Not quite nothing. Not quite nothing.
Space inside the false vacuum. Curved or warped. Small amount of energy contained in the curvature.
Ostensible violation of energy conservation. For sufficiently small time intervals. Allowed by the Heisenberg uncertainty principle. Bubble inflates exponentially. The Universe grows by many orders of magnitude in a tiny fraction of a second.