Here is a typical rv 50 amp plug. This is the same as many house appliances.
-The left and right poles are "x" & "y" which is for red and black positive wires (doesn't matter which is lt or rt).
- The upper straight pole is neutral- usually white wire.
- the lower D looking pole is ground- normally bare or green wire
The 50 amp- again 50 amp plug such as pictured above is wired the same for rvs and house 220. Each positive pole is 110 volts measure from 1 positive pole to ground, but if you measure across both positive poles with a volt meter the result will be 220 volts. The rvs internally just use each pole seperately, where house appliances use both poles combined.
AGAIN THIS IS FOR 50 AMP ONLY- RV 30 AMP IS COMPLETELY DIFFERENT THAN MOST 30 AMP (3 PRONG) HOUSE HOLD PLUGS.
Fyi- every individual line going into your house is 110 volts +- 5%