The figures below describe the main layout of a DSLR camera, it also illustrates the main parts of the camera.
Light enters to the camera through the lens. This light is reflected to the view finder by the mirror and Pentaprism. During the photo capture, mirror goes up and light falls on the optical sensor.
Below image shows the working of camera, and input light pathway
Below is a picture on the parts of a DSLR (Digital Single-Lens Reflex) camera. The difference between a DSLR and a normal camera is that DSLR has a bigger screen and you can preview the picture you took very clearly.
Lens is decides the filed of the view, below figure lists the parts of the lens.