Sigma 8-16mm F4.5-5.6 DC HSM is an Auto Focus (AF) Wideangle Zoom lens with APS-C / DX max sensor coverage. When mounted on a APS-C / DX sensor camera, it will give you an FF equivalent focal range of 12 - 24mm. With the max apertures of only f4.5 at 8mm, and f5.6 at 16mm, the lens is quite slow at both ends.
Sigma 8-16mm F4.5-5.6 DC HSM is not a weather sealed lens, so you have to be extra careful against rain and dust.