I have a lamp in my flat that can be turned on and off with two different buttons, how does a circuit look like to realize that?
The switch is normally referred to as Single-Pole Double-Throw. (SPDT) (I had to look that up as it is called different in my native language)
This in contrast to a standard on/off switch which is called Single-Pole Single-Throw (SPST).
As you can imagine there are many other types like. Double-Pole Single-Throw and Double-Pole Double-Throw.