Nikon 500mm f4D ED-IF II is an Auto Focus (AF) Telephoto Prime 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 500mm. With a max aperture of f4 at 500mm, this is a moderately fast lens.
Nikon 500mm f4D ED-IF II is not a weather sealed lens, so you have to be extra careful against rain and dust.