RV's have two distinctly different electrical systems. First is 120VAC, and as a general rule consists of all outlets, microwave, AC and refer, basically anything that you might find in your home. The 12VDC electrical systems consist of lights, furnace fan, water heater controls, refer controls. Some RV's offer an inverter, but unless you have a giant battery bank there are very few items that an inverter/battery bank can run without killing the batteries.
On top of the electrical systems you also have a gas system and a fresh water system, plus holding tanks and a drain system. It does take a lot of time to learn and understand each system. Take them one at a time, get familiar with it and then move to the next system until you are well versed in each one.