Canon 28-300mm f3.5-5.6L IS USM is an Auto Focus (AF) SuperZoom lens with 35mm FF max sensor coverage. When mounted on a 35mm FF sensor camera, it will give you an FF equivalent focal range of 28 - 300mm. With a max aperture of f3.5 at 28mm, we can not consider this lens fast on wide end and neither at tele end with its f5.6.
This lens features on optical image stabilization which helps capturing sharper images at lower shutter speeds. Canon 28-300mm f3.5-5.6L IS USM is weather sealed which makes it an ideal lens for outdoor use, especially when coupled with a weather sealed camera body.