Inverters basically give your stuff power. It's just a weird name because of how physics works. Don't worry about it so much.
Yeah, yeah, we all hear stories about how good science is or whatever but you know what? Like 75% of the time our day isn't made any better by knowing stuff like "how" and "why" and "quantum" and whatever words cutting edge scientists are doing. If you just want to watch cartoon while camping, all you need to know are the words "a magic box that turns a car battery into a USB port or whatever."
Now, that's not to say learning science is bad. We certainly support knowing as much as you can about everything. But we gotta be honest: how often are you, dear reader, going to use a Mobile Power Inverter to read the latest scientific journal or power a calculator of high importance? Face it, for what you plan to do with it, "Magic Box" is totally fine.