What is a 3-way switch and how does it function in controlling the lighting in a room?

A 3-way switch is a type of electrical switch that is used to control a single light fixture from two different locations. It has three terminals and allows for the light to be turned on or off from either switch. The switches are connected in a way that allows for the circuit to be completed regardless of the position of either switch, giving the user flexibility in controlling the lighting in a room from multiple points.