What is focal length?
Focal length is the measurement of an in focus object to the lens. A super wide-angle lens has the shortest focal length and a super telephoto lens has the longest focal length, see below for view ranges of focal length of different lenses.
Less than 20mm - Super Wide Angle Lens
24mm - 35mm - Wide Angle Lens
50mm - Normal Lens
80mm - 300mm - Telephoto Lens
More than 300mm - Super Telephoto Lens