A digital SLR, commonly known as a DSLR (Digital Single-Lens Reflex), is a type of camera that uses a system of mirrors and prisms to capture high-quality images. The design of a DSLR includes a lens, a movable mirror, and a prism that reflects the image into the optical viewfinder. When the shutter button is pressed, the mirror pops up, allowing light to reach the sensor and record the image.