Definition: Focal length is the distance from the center of the lens in the digital camera to the focal point. Focal length is measured in millimeters, and it's usually expressed as a 35mm film equivalent.
A lens that matches human vision with no telephoto or wide-angle capabilities applied to the lens is about 50mm. Wide-angle capabilities, usually considered anything less than 35mm, provides a larger field of view (FOV). Telephoto, or zoom, capabilities, usually considered anything greater than 70mm, provides a smaller FOV.
