As Dan pointed out, you have different electrical systems in your RV (120 volt AC and 12 volt DC).
The below is a copy and paste, and I usually recommend it to those just starting out. Some of it, you may already know, or may not be applicable to your particular RV. You will be able to filter out what pertains to your situation or not. I would suggest you read the electric threads and energy management first, and then the converter thread. This will help explain your different electrical systems of your RV, and how they operate...as well as what the converter does.
You can just peruse at your leisure:
Basic RV Electricity - RV Information (RV Maintenance)
Your very important converter:
RV Converters and Amp Draw - RV Information (RV Maintenance)
Suburban water heater (if applicable to your RV):
Water Heater bypass/crossover valves:
And the newest addition to help understand what constitutes a true full cylinder in refilling vs exchanging propane cylinders
Hope this helps.