If you got the kit lens with your DSLR camera like i did, its prob something along the lines of a 18 - 55mm zoom. This works as a real cheap entry level zoom that gets you all the way to 300mm and is ideal for wildlife photography.
Yes you need to shoot in good light as the 5.6 apature on the long end and the lack of IS will make images blur without a fast shutter.
I would argue its not for professional photographers but if you want to get your hands on cheap zoom then this might be a good option. Its light for a zoom with this range and the USM at least makes focusing decent.