What the polyvagal theory is
The Polyvagal Theory, in essence, is the science of how mammals connect, but also how they respond to danger. You've heard of fight & flight. Wellll, there's more to it than that. The PVT is the first to explain that there are actually three distinct primary states the body may be in:
Life threat response - allows for the end of life with little to no pain. Numbing and dissociation allow for possibility of escape.
Active when the internal or external worlds are perceived as life threatening.
Body numbs, dissociation, drop in blood pressure and heart rate.
Those 3 are just the primary states. It's also possible to have "mixed states," meaning the primaries are activated at the same time. Just like mixing primary colors creates another color. But you can't create a primary color by mixing other colors. They simply exist on their own.