Tamron 18-400mm F3.5-6.3 VC is an Auto Focus (AF) SuperZoom lens with APS-C / DX max sensor coverage. When mounted on a APS-C / DX sensor camera, it will give you an FF equivalent focal range of 27 - 600mm. With a max aperture of f3.5 at 18mm, we can not consider this lens fast on wide end, and it is slow at the tele end with its max aperture of f6.3.
Tamron 18-400mm F3.5-6.3 VC is weather sealed which makes it an ideal lens for outdoor use, especially when coupled with a weather sealed camera body.