We are going to go over the basics of how to wire a switch.
Let's assume you have an LED, a power supply, and a switch. You would like to be able to hook everything up and be able to turn you LED on and off with the switch.
We have a single pole single throw mini slide switch that we will be using for this example.
A switch provides a sophisticated way to simply "cut the power" and then "apply the power" back to the item. It is similar to simply cutting a wire and then splicing it back together, except now you can do it with a simple switch by moving the switch one way or the other.
With a single pole single throw switch (SPST) you will have a pole in the middle of the switch and one on one side of the switch as well. The middle part is where you can apply your constant power and then the other pole on the switch would have the wire that will go to your LED. You can switch either the positive or negative (ground) side of your circuit.