Microswitches

Design
Most microswitches have a single "Power" contact and either one or two other contacts. The other contact(s) can be Normally Open (NO), meaning that a circuit running through that contact is open/off until the switch is activated, or Normally Closed (NC), meaning that a circuit running through that contact is closed/on until the switch is activated.

Use
The primary use for microswitches with both NO and NC is to turn off one process as another turns on. For example, in an Electric Vehicle, at some point you want to turn OFF the drive motor and turn ON the brakes. Assuming both the drive and braking systems use the same voltage, you can run the drive motor through the NC contact and the braking system through the NO contact. That way, when the switch is activated, the drive disengages and the brakes engage.