Two phase power feeds most homes and businesses in the world. You can call it split phase, or twin phase, etc... but there's still 2 phases... Each of the 2 phases is 180 degrees out of phase with the other. At peak voltage from neutral they are double that from each other because one is positive and the other negative. The neutral leg in alternating current circuits does eventually end up as ground. The power company transmits the hot through wires and the neutral side through Mother Earth. The neutral is carried from the transformer on the pole to the load (home or business), for current balancing. However for current carrying capabilities, it should be the same gauge as the hot conductors. The ground wire in home wiring and cords usually is smaller gauge and not intended to be a current-carrying conductor.
What I saw was a standard, 2-phase, 220 VAC wiring scheme with a neutral and ground, just like the one I wired for my compressor. The power coming in is 2 - 110 VAC circuits that in my case had to be combined to give the me the 220 VAC I needed. This is truly simple. I do test when I go to parks, so I don't wind up with a fried converter or worse. The statement about not plugging into a 220 VAC outlet is wrong.... because it's the same as 2 - 110 VAC legs, which are needed for 50 amp RV service. The only instances in which they are used as 220 VAC is when the 2 hot wires are fed into the same load. In all other applications only 1 hot and the neutral is fed to the load. If you use a 50 to 30 amp converter to plug in, the converter continues only one of the 110 VAC legs into your RV cord. The other ends in the converter and does nothing.
Lots of misunderstanding by the electrically challenged... but lots of good info here, too... But hey... I'm not good at accounting, so don't feel too bad...