Forget about the ‘WAYS’ first concentrate on the ‘GANGS’
So, just think of a gang as a single switch, simple as. If your light switch has one ‘switch button’ on it then it’s a single (or 1) gang switch. If it has two ‘switch buttons’ on it then it’s a double (or 2) gang switch. etc. etc.
‘GANGS’ are easy, so what of their ‘WAYS’
Well, as far as light switches (or gangs) are concerned, they can only be one of two things; a one way switch or a two way switch, end of.
A one way switch has two terminals, its the simplest of switch arrangements. it’s either on or off, thats all it does. When it’s ‘ON’ the COM terminal is connected to the L1 terminal (let there be light!). When it’s ‘OFF’ the COM terminal is connected to nothing and (the switch is open) no current flows through the switch.
A two way switch has three terminals its a little more complicated (any useful) than it’s one way cousin. When it’s ‘ON’ (position 1) the COM terminal is connected to the L1 terminal. But when it’s ‘OFF’ (position 2) the current is diverted from the L1 to the L2 terminal. This is what we use in circuits when we want to be able to switch a single light on and off from two different switches (see the two way switching lighting diagrams).
So, by way of a little revision
If we have a switch with one “switch button’ (1 gang) it can have a switch mechanism that is either one or two ‘WAYS’ so we have two possible options;
1/ A single GANG one WAY switch or
2/ A single gang two WAY switch
If we have a switch with two “switch buttons’ (2 gangs) it can have a switch mechanism that is either one or two ‘WAYS’ so we have two possible options;
1/ A Double GANG one WAY switch or
2/ A Double gang two WAY switch