Several push buttons are popular in the Maker arena, including smaller and larger buttons that have legs that fit in a breadboard.
There's four legs so its mechanically more secure when soldering in place on a circuit board, but it doesn't have two switches in it!
There are connections between some of the legs. a is already connected to d and b is already connected to c.
In the diagram below, you can see the hookup of the switch (the switch is circled in green) as a standard normally open switch. The opposite corners are connected (a and c) to ensure we have a single pole normally open switch.