Panasonic 100-300mm F4-5.6 OIS is an Auto Focus (AF) Telephoto Zoom lens with FourThirds max sensor coverage. When mounted on a FourThirds sensor camera, it will give you an FF equivalent focal range of 200 - 600mm. With a max aperture of f4 at 100mm, we can not consider this lens fast on wide end and neither at tele end with its f5.6.
This lens features on optical image stabilization which helps capturing sharper images at lower shutter speeds. Panasonic 100-300mm F4-5.6 OIS is not a weather sealed lens, so you have to be extra careful against rain and dust.