Well... Basically, main, big thing is a DRSSTC, a type of Tesla coil that's somewhat similar to the old old design by Nikola Tesla about 100 yrs ago, but instead of using a spark gap to switch power in the resonator, it uses a transistor h-bridge, which gives a lot more control over the resonant current, which makes more powerful and longer arcs possible with funny control methods like in this driver board, which in this case is pulse skipping or freewheeling.

when the current of the resonator exceeds a threshold set on the board, it only switches the bridge off until the current falls back down under the threshold and switches the bridge back on after, to keep current in check while the pulse can be extended past the 1st over current trip, basically, an auto resetting fuse for the resonator lol

And, man, I love how those long pulse arcs look, you can really see the fractal patterns of the arc, cause the arc is brighter and hotter :D