Olympus ED 12-40mm f2.8 PRO is an Auto Focus (AF) Standard Zoom lens with FourThirds max sensor coverage. When mounted on a FourThirds sensor camera, it will give you an FF equivalent focal range of 24 - 80mm. With a max aperture of f2.8, this lens is fast on wide end and equally fast at 40mm with a max aperture of f2.8.
Olympus ED 12-40mm f2.8 PRO is weather sealed which makes it an ideal lens for outdoor use, especially when coupled with a weather sealed camera body.