The switch handles AC voltage of 125 or 250 volts, so clearly intended for mains use so and that means we need to be a little careful.
Four Poles means four terminals, the metal lugs sticking up underneath. These are the cause of the confusion. Most people would visualise a switch as having just two terminals, but four makes things more tricky.
Well this switch is illuminated. It has an internal light, probably an LED or Neon light, which comes on when the switch is closed – but only if the switch is wired properly. So the switch needs two poles for the electrical current to come in and go out of, and the light needs two poles, to provide it with electricity.
In a circumstance like this, it's much easier to SHOW how to do it than describe it, so I'd urge you to watch the video below. This gives a real life demo that will hopefully make things nice and clear, but if you have any questions, feel free to drop me a line.