What's the difference between a Digital Camera, and an SLR camera?

There are three types of digital cameras.

A regular digital camera, or common compact, uses a
built-in small lens and a sensor for forming the
image. You can preview the image on the back LCD or
through an optical eyepiece which has a separate lens
(for those times when you can't see the image on LCD
due to darkness or when you want to save battery).
These cameras are cheap, small, and image quality is
sacrificed for size. This includes a poor image
processor and also parallax error when focusing
through the eyepiece (because the eyepiece is on a higher level). Also a common problem is the red-eye effect because of the compact format since the flash is too close to the lens.
For most problems the compact camera compensates through heavy image processing which usually makes the final image less than appropriate for editing.

A SLR camera (single lens reflex) uses a mirror in front of the sensor to reflect the image to the eyepiece so that the user sees everything just as the camera does, allowing for precise focusing. Also they are bigger as they host high tech components such as dedicated image processors which allow for better image quality. Also the lens is separated from the camera body, allowing greater flexibility by being able to change the lens as the situation demands it (wide angle lenses to capture more of a landscape or telephoto lenses for far away subjects). This system is better as a dedicated lens work perfectly for the purpose it was made as opposed to a small general purpose lens that tries to do everything and fails. SLR cameras also allow for great manual control, longer exposures so that the camera is able to take a good picture in any circumstances (provided the user uses appropriate settings).

digital camera has no moving parts when it comes to image saving.
slr involves a shutter opening up and light creating an image onto sensitive film.
digital slr is a combination. it has moving parts but the image hits a sensor instead of film that creates the image onto some sort of storage solution like a removable disk/card.
digital slr is the best!! but $$$

go to howstuffworks.com
it will show you

A digital camera is one that captures, process and displays an image electronically while a film camera uses film to capture the image and uses chemicals to process it (developing). An SLR on the other hand could either be digital or a film camera. The main feature of an slr is the mirror on the back of the lens which reflects the image to the viewfinder so that the person using the camera can see the actual image before it is captured. This mirror flips out of the way when the shutter button is pressed thus letting the light to fall on the sensor (for digital) or film (for film camera). An slr has interchangeable lens and usually has more manual controls than point and shoot cameras. A digital slr is referred to as dslr.