Learning how thunderstorms work is something I think everyone should do on a basic level - they are utterly fascinating. What is amazing to me is that these repeatable and frankly amazing structures are created out of nothing but air, water, and heat in varying combinations.
In layman's terms (and while I'm a layman I'm educated enough to be able to say that) a thunderstorm is simply caused by buoyant air rising. As it rises, the moisture inside of the air condenses, creating a cloud and releasing heat (latent heat). That warms the "parcel" of air more (another term he used frequently) and it rises faster.
Air that rises sucks up more air from below it because it creates a low pressure region. Eventually the air hits the top of the troposphere, which is stable (stable means that the air is warmer than the rising parcel and the rising air is no longer buoyant. Keep in mind that "warmer" is relative and can mean -60F.)
In conditions that cause a storm like this to form, vertical wind shear is important. In a pulse thunderstorm, the downdraft (the rain cooled air) gets in the way of the updraft and chokes it off. But the wind shear not only causes the updraft to rotate, it pushes the downdraft out of the way of the updraft, so nothing chokes it off. This is why when you look at a supercell, it is nearly always tilted to the direction of travel. (mesocyclone is another word for updraft in this case.)
Now that the storm is created, you have room for the other factors he was mentioning, such as the RFD, FFD, etc. Basically there is a certain combination of factors required to set the air at the ground to spinning. The interesting thing about this simulation was that the managed to find the sweet spot and get their simulation to create a long-tracked tornado. Much of his presentation was spent highlighting certain parcels of air and showing how they got ingested by either the meso or the tornadic circulation (which are related but not necessarily the same thing.)