A three-way switch is a type of electrical switch that allows you to control a single light or set of lights from two different locations. This is particularly useful in large rooms or hallways where you want to turn the lights on or off from either end. In a typical setup, two three-way switches are connected to the same light fixture. Each switch has three terminals: one common terminal and two traveler terminals. When you flip either switch, it changes the path of electricity, allowing the light to turn on or off, regardless of the position of the other switch.