This is essentially the same as molten salt reactors.  It will not burn Thorium directly as Thorium 232 is NOT fissionable.  So it requires a fissionable isotope of Uranium or Plutonium to get things started.  Thorium 232 then absorbs a neutron to become Thorium 233, and then beta decays to Protactinium 233, which beta decays again to become Uranium 233 which is fissionable.  What is not stated in this video is that these reactors can fission most actinides because actinides are fissionable with fast neutrons generated in these reactors so the waste products that are left are only fission products and these all have half-lives that are short transforming a 500,000 year waste problem into a one or two hundred year waste problem and a waste volume less than 1/100th that of a conventional light water reactor.