A camera lens (also known as a photographic lens or photographic objective) is an optical lens or assembly of lenses used in conjunction with a camera body and mechanism to make images of objects either on photographic film or on other media capable of storing an image chemically or electronically. We have a wide lens for clicking wide-angle pictures whereas we also can get a macro lens to click close-ups of different objects.
There is no major difference in principle between a lens used for a still camera, a video camera, a telescope, a microscope, or other apparatus, but the details of design and construction are different. The focal length of a lens is calculated in mm, a higher number in mm of a lens means that it can zoom more. The lower number means that it can take wide-angle shots which would not be possible on other lenses. On a higher number of lenses, higher than 50mm means that the focus will be on a smaller aspect of the view.