Ghost ring sights are basically thin iron rings that are installed on top of most submachine guns and combat shotguns. There are no optical or laser sights used in this case. It is just a ring that the shooter looks through in order to align their target through the middle of the ring. There is also a thick post in front of the ring so you can aim at your target more precisely.
Ghost rings are the perfect sights to have if you want to remain discrete in your targeting. It is truly a clever way to attack your target by surprise, which comes in handy when hunting or in war type situations.