What is the difference between digital camera and DSLR camera?

DSLR stands for " digital single lens reflex" and are the modern equivalents of the film based single lens reflex cameras. As the name suggests, they are digital and use an electronic sensor as any other digital camera does.
The difference between DSLRs and other digital cameras is in the way the photographer sees images in preparation to take a picture.

A single lens reflex camera uses a mirror positioned behind the lens to direct the light onto a viewing screen. The viewfinder delivers an image using the same lens as that used to capture a picture. When the shutter is released, the mirror moves out of the light path, the image is captured and the mirror returns to its normal position. The photographer sees the viewfinder go dark for a fraction of a second.

Other digital cameras use a separate optical viewfinder or have a display on the rear of the camera that shows whatever the sensor is viewing.

A DSLR tends to be much larger than other types of digital camera but they share many features such as auto-focus, auto--exposure, manual overrides and so on. The SLR is designed to be a robust and flexible camera and generally there will be a wide range of lenses and other accessories that other compact digital cameras do not have.

Although many compact digital cameras produce excellent pictures and are of outstanding quality, the DSLR is the camera that lends itself to the professional and serious amateur photographer by providing flexibility and because of the accuracy of the viewfinder compared to those of a compact camera.