Sigma 200-500mm F2.8 EX DG is an Auto Focus (AF) Telephoto 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 200 - 500mm. With a max aperture of f2.8, this lens is fast on wide end and equally fast at 500mm with a max aperture of f2.8.
Sigma 200-500mm F2.8 EX DG is not a weather sealed lens, so you have to be extra careful against rain and dust.