If you're wondering what is a DSLR camera in the first place, it stands for 'digital single-lens reflex.' Cameras in the DSLR category use a mirror that sits inside the camera body, between the back of the lens ahd the film plane and shutter. The mirror reflects the image coming in through the lens for the eye, and then flips up out of the way to let the light through the shutter and onto the digital sensor when the shutter button is pushed.