This document provides information about three-way and four-way switches: - It defines single pole, single throw (SPST), single pole double throw (SPDT), double pole single throw (DPST), and double pole double throw (DPDT) switches. - It explains that three-way switches have three terminals and are used to control lights from two locations, while four-way switches have four terminals and control lights from more than two locations. - The document demonstrates how a circuit works using two three-way switches and one four-way switch to control a light from multiple locations.