Inflation is a prequel to the conventional Big Bang theory. ...It does provide a theory of the propulsion that drove the universe into this humungous episode of expansion which we call the Big Bang. The Early Universe (2012)
In short what I like to say is that the Big Bang says nothing about what banged, why it banged, or what happened before it banged. It really has no bang in the Big Bang. It is a bangless theory, despite its name. The Early Universe (2012)