A brief overview of three types of light switch, then an example of each is dismantled to see how they work inside.
A one way switch has two terminals. In one position the terminals are connected together, in the other the terminals are not connected.
Used for normal lighting circuits with a single switch controlling one or more lights.
These have three terminals, usually marked C, L1, L2. In one position C and L1 are connected, in the other C and L2 are connected. L1 and L2 are never connected together.
Used where two switches control the same lighting.
These have four terminals and are equivalent to two 2-way switches combined. There are various labelling schemes but L1, L2, L3, L4 is common. In one position L1 connects to L3, L2 connects to L4. In the other position L1 connects to L4, L2 connects to L3.
Used where three or more switches control the same lighting.