Let me draw you a picture:
Shore power.. Your useing a hand drill and it shorts hot to case the 3rd wire is broken off (of course) so you could plug into a 2 wire outlet at home:
Transformer---Stuff---Hot wire-----case/YOU---_Ground---Return to transformer (Been nice knowing you) Stff is your meter, breaker box, and so on but for this it's all part of the hot wire.
now let's use the generator (or inverter) to power that same shorted drill
Hot wire----Case/You---Ground (Tthat is all folks there is no return path to the generator/inverter you are protected and continue to breath.. In fact the drill works normally and you finish the job.
