How does a dual light switch work?

That’s called a 3-way switch here where I live, Here’s a link describing how they work. https://home.howstuffworks.com/three-way.htm

That is called a Single Pole Double Throw switch or SPDT. Learn that one and you can fix most things having to do with house wiring. I keep a couple of spares at home and one in my tool box just in case.

A somewhat simplistic explanation. You have two different circuits connecting to each switch. To complete either circuit, both switches have to connect to the same circuit. Each time you flick a switch you alternate between completing one of the circuits (causing the light to go on) and opening both circuits (causing the light to go off).

A lot of it has to do with the wiring itself and the wire cable serving both switches and the light has to be three strand instead of two. (One black wire, one white wire, and one red wire.)

I read an article because I had no idea. The most interesting thing about it is that the toggles on the wall are not labeled with the words on/off. It seems like I would have noticed that in my years of living in two story homes.

We have two sets of lights in the house that have THREE switches.

I have an outlet with three switches.

I know @JLeslie has already answered this but yeah two switches to control a light or outlet are 3-way switches. But if you need three or more switches to control the same lights or outlets you need 4-way switches wired in between the 3-way switches. You can have an unlimited number of them just in case you wanted to know .