If you have a cabin or an RV that's wired for electricity, but you don't have any power coming in on the mains, or you don't have mains, you can backfeed the system by plugging your generator into one of the outlets.

The proper thing to do is to use a special outlet that's made for a generator, and perhaps an isolator switch as well, but if you don't have those then you might think to yourself, why don't I just make a male to male plug? It definitely works, but it's also dangerous if you or anyone unplugs it while the system is hot.