On other type of switch is typically used in camera shutter releases where you press the shutter 1/2 way and the camera focuses, and if you press it all of the way, it takes a picture. I don't think I have a picture of a wired shutter release disassembled, but a wired shutter release has 3 wires leading out (ground, focus, and shoot). Internally there is 3 pieces of metal held apart with a small spring. When you press the button down 1/2 way, it connects the ground and focus wires. If you press the button down all of the way, the ground, focus, and fire wires are all connected.
The camera has a small circuit that becomes active when the focus + ground wires are connected, and another for the shoot + ground wires. Some cameras need the focus wire to be connected as well, others don't, which can become important if you are trying to trip the shutter from an Arduino.