DSLR Digital Single Lens Reflex
See SLR below. DSLRs are similar in design with an exception that the method of capturing the image is digital in nature rather than using photographic film. As photographic film is becoming more and more redundant, most SLR cameras are now DSLRs. There may come a time when people drop the ‘D’ and refer to their digital SLR camera as an SLR.

SLR Single Lens Reflex
This refers to a particular design of photographic film stills camera. What makes this design special is that with some other designs of camera the photographer looks through a viewfinder lens that is separate to the lens that will end up taking the photograph. As there is a difference in the position on the camera of the taking and viewing lenses, the photographer will see a slightly different view (known as parallax error) that will actually be taken. So the photograph doesn’t aways come out framed in the way the photographer intended. With an SLR camera the light entering the camera via the taking lens is diverted and reflected in to an eye piece so that the photographer can see exactly what will fall upon the film. This removes parallax error and means the photographer can be sure that why they see through the camera viewfinder is what will appear on the film. At the moment the shutter release button is pressed, a mirror flips up out of the way allowing the light passing through the lens to fall upon the film (rather than being diverted to the eyepiece). The mirror flipping results in a particular sound that many recognize as coming from an SLR camera.