Panasonic 100-400mm F4.0-6.3 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 - 200mm. With a max aperture of f4 at 100mm, this is a moderately fast lens.
This lens features on optical image stabilization which helps capturing sharper images at lower shutter speeds. Panasonic 100-400mm F4.0-6.3 is weather sealed which makes it an ideal lens for outdoor use, especially when coupled with a weather sealed camera body.