Technically, not all digital cameras are SLRs. The term SLR (single-lens reflex) refers to a camera whose viewfinder and capture device (film, CCD chip, or CMOS chip) use the same main lens. Since normal consumer digital cameras usually have a viewfinder that uses a different lens than the one that the CCD or CMOS does, they cannot technically be referred to as an SLR, because they do not have the reflex action that reflects the image up to the viewfinder from the main lens. However, most digital cameras do have an LCD screen on the back that shows you what the sensor is seeing through the main lens. So you can see how the subject matter will be framed in the final shot without any parallax error. And you can also get a general sense of the focusing and DOF. However, there is a limit to the number of pixels that the lcd screen can show. The sensor can capture many more pixels than the screen has, so you don't get to see all the information in the image when you look at it. This is where the advantage of a true digital SLR comes in. The viewfinder on a DSLR is basically the same as on a film SLR camera. It is optical, not digitial. With an SLR, your eye is seeing the shot without the LCD in the middle, which means you can see much more detail since your eye can see more information than an LCD would display. The advantage of this is that you can get a better sense of the focusing and depth of field when you see the shot optically than digital. DSLRs are especially useful when the camera has interchangable lenses, since then a separate viewfinder would not necessarily show what the lens is seeing, and the LCD display would not show you precise depth of field and focusing. So basically, no; technically not all digital cameras are SLRs, although in practice they kind of have a similar effect because of the LCD screen, but as you get more advanced in photography and need more accuracy in framing and focusing your shots, the separate viewfinder and LCD are not enough and you need an SLR viewfinder. I hope this clarifies the subject a bit.