Telephoto lenses can provide you with a narrow field of view. These long lenses enable you to compress a distance (and compress the sense of depth, as well) and pick out specific objects from far off. They have a strong resolving power and an inherent shallow DOF, where the slightest lateral moment can take a subject out of view. Telephoto lenses are great for wildlife, portrait, sports, and documentary types of photography. They enable you to capture subjects from hundreds of feet away.
Photograph taken by DigitalMate 85mm f/1.8 Aspherical Medium Telephoto Lens