The Blackbird, fly is a twin-lens reflex camera: one lens is used to expose the film, while the other is used like a viewfinder. It's a famous style of camera whose history stretches back to the 1920s. The Blackbird fly uses 35mm film.
There are two ways to take a picture with the Blackbird fly. For quiet and reflective framing, you can hold the camera at waist level and look down, to compose your shot using the finder lens. For a quicker style of shot, you can use the sportsfinder, which approximates a viewfinder through a notch in the top of the camera.
The Blackbird fly can take pictures in standard 35mm film format (24x36), but using a different (provided) mask, it can also produce square format pictures (24x24). You can even remove the mask entirely and make a larger square format image (36x36), which fills up the entire width of the 35mm film, including the side sprocket holes.
For shooting during the day, you can alternate between apertures f/7 and f/11, with a shutter speed of 1/125. At night, you can switch the shutter to B-mode to let in as much light as you might need, or you can also attach a flash for even more possibilities.
Variable focusing, from 0.8 meters, makes for a sharp subject. The Blackbird fly uses a wide-angle 33mm lens and also allows you to take multiple exposures on the same frame.