First, you need something that can collect the sounds from your body like a funnel, half of a plastic bottle, or a small cup. Then you need something so that the sounds can travel from your collection device to your ears like some kind of rubber or plastic tubing. With your stethoscope you can try to listen to your heart beat and you can try it on your parents too. All cameras work on the same basic principles, and these have parallels with the human eye. The human eye needs light to see.
Light enters the eye through the pupil, and the pupil is made larger or smaller by the iris.
The light falls on the retina, which sends information to the brain that tells it what you are seeing. Similarly, the camera also needs light to see. The light falls on the film, which contains a chemical mixture sensitive to light. The mixture captures the image that the camera shoots.