A wide angle lens is one that takes a photo of a wider image area, and a telephoto lens is one that features internal elements that shorten the length of the lens body while still allowing for a longer focal length. A wide angle telephoto lens combines these elements, and these lenses can come in a wide variety of focal lengths. Choosing the best wide angle telephoto lens starts with determining which ones will work with your particular camera; The mounting system can differ among camera manufacturers, so you will need to make sure you buy a lens that is made specifically for the brand of camera you own.
The technology included in a wide angle telephoto lens has advanced significantly over the years, especially since the advent of digital photography. Such lenses are designed to work with single lens reflex (SLR), camera bodies, and the digital version of these advanced cameras are known as digital single lens reflex cameras (DSLRs). Be sure the lens you are considering is made for a DSLR if you are shooting digital, as many lenses made for film SLRs will not work with digital camera bodies. Sometimes a wide angle telephoto lens designed for use with an SLR can be used with a DSLR, but some functions such as autofocus and image stabilization will not work properly.
Once you have narrowed down your search to lenses that will work with your brand of camera, think carefully about your budget for purchasing the lens as well as what features you absolutely need. Almost all DSLR lenses feature autofocus capabilities, but not all feature image stabilization. This feature prevents blurring from camera shaking when the lens is zoomed all the way in, and it can mean the difference between a great shot and a mediocre one. Expect to pay more for a wide angle telephoto lens with image stabilization capabilities, however.
The focal length of the wide angle telephoto lens can vary significantly as well. This will affect how far in and out you can zoom to capture images. A lower number means a wider field of view, while a higher number means a more zoomed, narrow view. A lens that measures 10-20, for example, means the focal length at 10mm will capture a fairly wide image, while the 20mm focal length will capture a narrower image. The larger the difference between the numbers, the more the lens will zoom in and out, adding to the versatility of the lens.