system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 - How does a light with two switches work? Like the light at the top of the stairs might have a switch at the bottom and at the top

If one switch is on and the other is off the light is on, but if both are on or both are off the light is off. How does it work?
gpt
In order for current to flow, you need to have a complete circuit. A normal light with a single switch is just one loop of wire. When the switch is off, the loop is open. When the switch is on, the loop closes and completes the circuit.

For the double switch lights, it's still a complete circuit, but it has two switches. In between the two switches there are actually two paths - let's call them Path A and Path B. Instead of opening the loop or closing it, each switch controls whether it is connected to Path A or Path B. When they're on the same path, there's a complete circuit and the bulb lights up.

So if they're both on Path A, the light is on. You can turn the light off by flipping one switch, because now one switch is on Path A and the other is on Path B. If you want to turn the light on, you can flip either switch - putting them both on Path B, or putting the first switch back on Path A.