A DSLR (Digital Single-Lens Reflex) is a type of digital camera known for its optical viewfinder system and the use of interchangeable lenses. The term "Single-Lens Reflex" refers to the mirror reflex system inside the camera that directs light through a single lens to both the viewfinder and the image sensor.

In a DSLR, incoming light is directed through the lens onto a movable mirror. This mirror then reflects the light into the optical viewfinder and/or an autofocus sensor. When the shutter button is pressed, the mirror flips up, and the light hits the digital image sensor directly, capturing the image.

DSLR cameras are popular among professional and hobby photographers alike because they offer high image quality, fast performance, various manual control options, and the ability to use a wide range of lenses and accessories. This versatility makes DSLR cameras suitable for various photographic situations, from portraits and landscapes to action and macro photography.

This type of camera technology is increasingly being replaced by mirrorless system cameras (MILC - Mirrorless Interchangeable Lens Camera).