Sigma 18-125mm F3.8-5.6 DC HSM is an Auto Focus (AF) SuperZoom 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 27 - 187.5mm. With a max aperture of f3.8 at 18mm, we can not consider this lens fast on wide end and neither at tele end with its f5.6.
Sigma 18-125mm F3.8-5.6 DC HSM is not a weather sealed lens, so you have to be extra careful against rain and dust.