system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do lights with multiple light switches work? How is it that flipping one switch on when the light is already on turns it off?
gpt
The 2 light switches are connected via 2 wires. Call them wires A and B.

If switch 1 is on wire A and switch 2 is on A, the light is on. 

If switch 1 is on wire B and switch 2 is on B, the light is on. 

If switch 1 is on wire A and switch 2 is on B, the light is off. 

If switch 1 is on wire B and switch 2 is on A, the light is off. 


Having both switches set to the same wire completes the circuit.