This class is basically a rudimentary state machine, the states are set by calling rightVolcanRotate(), rightVolcanStop(), leftVolcanRotate(), and leftVolcanStop(). Those methods are invoked by the leap motion unity SDK (4.5.0)
https://developer.leapmotion.com/unity#5436356
The leap motion SDK exposes some unity events for some gestures, eg: left hand opened, right hand opened, the Animation's methods are invoked when those events happens. For more details I recommend to play around with the leap sdk.