Sigma 14-24mm F2.8 DG HSM Art is an Auto Focus (AF) Wideangle Zoom 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 14 - 24mm. With a max aperture of f2.8, this lens is fast on wide end and equally fast at 24mm with a max aperture of f2.8.
Sigma 14-24mm F2.8 DG HSM Art is weather sealed which makes it an ideal lens for outdoor use, especially when coupled with a weather sealed camera body.