Single pole switches are most commonly used in home lighting circuits to control one or more lights or fixtures from a single location, such as the entrance to a room. Three pole or three-way switches are used to control one or more lights or fixtures from multiple locations, such as the top and bottom of a flight of stairs.
Single pole and three pole switches look the same when installed but are used for different purposes. Closer inspection reveals that while a single pole switch has two terminals, a three pole switch has three.