Figure 1: Bigshot's viewfinder (touch or hover to zoom)
The viewfinder of a camera is a small "window" that the photographer looks through to see the field of view that is captured by the camera’s lens. It allows the photographer to frame a scene before taking the photo.
The viewfinder is usually a separate set of lenses that is located above the camera’s lens. Unlike the camera's lens, it is not designed to converge light to form an image on its own. Rather, it works together with the lens inside the photographer’s eye to form an image on the retina of the eye. Figure 1 shows a photographer looking through Bigshot's viewfinder. Placing the cursor on the figure (or touching it) will reveal the lenses of the viewfinder and the structure of the eye.