If you remember high school at all, you may recall building your own camera in science class. The type most people made were pinhole cameras. These are basically light-tight, small cardboard boxes with a small hole for a lens. Students were taught how to make them to learn the basics of photography.
The box usually has a piece of film or photographic paper attached into the other end of it. The shutter is generally made of a flap of cardboard with a tape hinge. The pinhole can be made by inserting a sewing needle through a thin piece of tinfoil, aluminum or brass sheeting. You then tape the foil to the inside of the box behind a hole which is cut through it. To change the angle view of the camera, a sliding film holder or back is used so you can adjust the distance between the film and pinhole. By moving the film closer to the pinhole you get a wide angle field of view and a shorter exposure time. If you move it away from the hole the result is a telephoto or narrow angle view with a longer exposure time. You can then figure out the focal length and f stop and take photos by letting light in through the lens.
Versions of pinhole cameras are used today in artistic photography and for surveillance and security systems. You can buy pinhole cameras starting at about $50.