Your RV has two different electric systems. The 12 v system is powered by your batteries when unplugged, your Converter/charger when plugged into shore power. The Converter/charger not only charges the batteries but also provides power to lights, thermostat, refrigerator, water heater, etc. A battery disconnect switch usually disconnects most functions of 12 v house power, but not all, so leaving RV in storage could still discharge batteries.
The 120 v system is powered by the shore cord plugged into an appropriate outlet. When unplugged, the only way to get power to the outlets would be to an Inverter installed. They change 12 v direct current to 120 v alternating power. They deplete batteries quickly and aren't a replacement for a generator.
You may wish to read more here:
The 12volt Side of Life (Part 1)
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