How do power generators work? I mean the practical application, not the actual inner workings of the machine.?

Normally, an auxiliary generator where there is frequent need for it requires automatic start up, interlock between the mains supply and the house power and fuel supply engines. And it must be outdoors. Since it is difficult/expensive to have a generator that meets all the needs of everything in a living place, normally changes must be made to the wiring so a portion of the house containing vital stuff is picked up by the generator - food preservation, lighting, computers - and the stuff that can be dropped is left off - dryers, ovens, heavier tools - is left to die. Obviously, choices would be make in each case - a seriously ill person might require air conditioning and breathing assistance, a glass facility might maintain the melted glass.

This means it is almost impossible to function if you live in an apartment. The alternative in such a location is to buy individual Uninterruptible Power Supply (UPS) units which contain a battery, recharging circuits, AC generation and switch over. Analysis of needs will show what size is needed and where they might be placed. The one I have on my computer is rather small, but the failures we have here are almost always just a couple of minutes at most, so my computer does not shut down and if the power does not seem to be coming back I have time to shut down smoothly so I don't have damaged files.