The focal length of a lens determines how much magnification it provides. A lens with a shorter focal length will be able to "see" a wider view of a subject than can a lens with a longer focal length, which would see a narrower view of the scene, but at a higher level of magnification. Whether a lens seems to be a wide angle or telephoto lens depends on the size of the image sensor it is used with. As a result, one can not say that a given 15mm lens is wide, or that a 200mm lens is telephoto in nature since the size of the image sensor is not known. When speaking of lenses used on 35mm film systems, 35mm of focal length or less is typically considered wide, and 80mm or longer is generally considered telephoto. Digital cameras often refer to their lenses as being "equivalent" to a particular 35mm film camera lens in focal length to give people an idea as to how wide or telephoto it acts when paired with that particular camera's sensor.
fixed focus
focal point