A viewfinder is the small window or screen on a camera that you look through to see exactly what your picture will capture. When photographers raise a camera to their eye and peer through that little opening, they're using the viewfinder to frame their shot, deciding what to include and what to leave out.

On older cameras and many professional cameras today, the viewfinder is an actual glass window that shows the scene in front of you. On digital cameras and smartphones, the viewfinder is often an electronic screen on the back of the camera, though some photographers prefer the traditional eye-level kind because it helps them hold the camera steady and focus on composition.

The viewfinder helps you make important choices before you press the shutter button: Is your friend centered in the frame? Is there a distracting trash can in the background? Should you move closer or step back? A good photographer learns to use the viewfinder like an artist uses a canvas, carefully arranging all the elements.