EF-S 17-85mm f/4-5.6 IS USM includes wide-angle, standard and telephoto focal lengths in a single lens.
WIDE-ANGLE AND TELEPHOTO
Lenses with small focal lengths have wide angles-of-view and are called wide-angle. Those with long focal lengths have narrow angles- of-view and are called telephoto (because the narrow angle has the effect of making the subject appear closer than it really is – ‘tele’ is Greek for ‘far off). In between are standard lenses, which have an angle-of-view similar to that of the human eye (usually taken to be around 50mm for photographic applications). So if you are shooting a landscape and want to include a wide expanse of the scene, you need a lens with a short focal length – between 24mm and 35mm is popular. Wide-angle lenses are also good indoors – you can include a lot of the subject even when there is no space to move back. Telephoto lenses, on the other hand, are useful when the subject is distant and you can’t move any closer. These lenses, with focal lengths from 70mm to 800mm, are popular for wildlife, sports and news.