What are you trying to switch?
A Single-pole, Single-throw (SPST) switch has two contacts. It would typically be installed in series on the hot (powered) side of the circuit- which is usually fused. You cut the hot lead and connect the switch. The switch then simply completes or interrupts the circuit.
A Single-pole, Double-throw (SPDT) switch will have three contacts. The hot would go to the center connection and the two items to be switched would go on the others. In this case when the switch will complete one ciruit or the other depending on which way it is thrown.
The there's the Double-pole, Double-throw (DPDT)switch that has 6 terminals, and auxiliary relays for switching higher current items....and on and on.
Give us a bit more info.
AL
