Switches really don't need any introduction. It simply connects and disconnect a circuit. This section gives an overview of the contact configurations.
There are 3 commonly used configurations: SPST, SPDT, and DPDT.
SPST = Single Pole, Single Throw
This is a two terminal switch that opens and closes a circuit.
SPDT = Single Pole, Double Throw
This is a three terminal switch that connects one terminal to either of the other two.
DPDT = Double Pole, Double Throw
This is a six terminal switch that connects a pair of terminals to either of the other two pairs.