Get you soldering iron and let’s have fun with switches.
After soldering this simple circuit, I started playing with the switches. At first it felt like magic because sometimes the light went on and sometimes it did not. I played some more and started to see that any of the two switches can control the other switch.
If I decided that switch two must have control I left switch one on now switch two can switch the lamp on and off. If I decided to give switch two no control I just left switch one off now switch two have no control.
I figure mains switches is wired in series with the rest of the circuit if you switch the mains switch off the rest of the switches have no power on them if you left the mains switch on the rest of the switches will work again.