Canon 35mm f1.4L USM is an Auto Focus (AF) Wideangle 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 35mm. Providing a max aperture of f1.4 at 35mm, this lens is very fast.
Canon 35mm f1.4L USM is not a weather sealed lens, so you have to be extra careful against rain and dust. Canon 35mm f1.4L USM was replaced with Canon EF 35mm F1.4L II USM. Follow the link to read our comparison of these cameras: Compare Canon EF 35mm f1.4L USM vs Canon EF 35mm F1.4L II USM