Where does it come from?
Generator: There are on-board and portable generators, most people if they do not have an on-board one look for a portable one. When it comes to portable ones, there are two types of generators, noisy and less noisy. You want to own and use a less noisy one, aka and Inverter Generator. You do NOT want to own or use a generator that would be used at a work site, your fellow campers will HATE you for it. There are multiple manufacturers out there who make inverter generators, most of them you can be standing next to the generator with someone else and be able to carry on a normal conversation. My preference throughout the years have been the ones manufactured by Honda but do your research.
Inverter: What is an inverter? It takes battery power (Direct Current, which you can read about in Chapter 4), and makes 120 volts of Alternating Current (AC). You can find all kinds, makes, models, modified/pure sine wave but the most important thing you need to know is what do you want to power and how many amps or watts does it pull? You then will need the size inverter to handle that and most importantly the size of copper wire to hook to battery that can support the inverter. Read more about inverters and other goodies in Chapter 9 Advanced Electricity.
Shore Power: You will hear this term; reality is it is a boating term but RVers have adapted it. What is it? It is where you plug into a campground or your sticks/bricks home, those are the two most common ones, aka commercial power.