Identify live or neutral in 2-way switch
A SPDT is like an XOR logic gate. The sector can only exclusively selector 1 or the other which in logic inverts the output (on/off).
For electricians, the 3 wires is related to the switch name &quot;3-way&quot;  , for Engineers we simply them SPDT. And for students of logic an &quot;XOR switch&quot;...



simulate this circuit &ndash; Schematic created using CircuitLab