There are two types of digital camera, SLR and Compact Camera, this is the differences…

Compact Camera: The simple camera we have all used, small and portable. It has a lens through which the image is projected onto the film, and a second simple eyepiece lens through which the user composes the image, seeing APPROXIMATELY the image that will form on the lens.

SLR=Single Lens Reflex: these cameras have a single lens (that is interchangeable) and, by means of a mirror behind the lens, and a prism above the mirror and in front of the eyepiece, project the image directly from the lens to the eye of the user to compose their image as they wish.

The SLR Camera has many features, such as: most use 35mm film: cheap, versatile, widely available, easily processed, and enough quality for A3 prints; as much quality as most need.

Interchangeable lenses:
There are far fewer compromises made with SLR lenses because they don’t need to do very many different jobs in one as a zoom on a compact camera does. Therefore SLR lenses are generally of the very best quality.

Total creative control:
Compact cameras make almost all of the decisions about how a photograph is taken for you.
SLR cameras have the capacity to set every aspect of a photo yourself. Autofocus SLR cameras have automatic settings if you require them, but you can always use them totally manually, choosing every setting yourself: it remains your choice, something you don’t have with a compact camera.