3-way switch is the type of switch is installed to control a luminaire from two different control points. Two switches are needed and it is a SPDT switch.
Step-by-step explanation:
A single pole switch helps in operating one or more luminaires from one location. In order to have access to a luminaire from two different place we can use 3 way switch. It is a single point double throw switch type and uses two switches one at each locations.
For allowing the flow of current in the circuit the circuit must be completed and it will be achieved only when the both switches are up or down. When we need to control the load at two different places, we can use three way switches. It will have a common terminal and two traveler terminals.