You asked
What is the sony fe 28 70mm f 3 5 5 6 oss good for?
The Sony FE 28-70mm f/3.5-5.6 OSS is a sensible everyday standard zoom for full frame Sony E cameras. It covers wide-angle to short-telephoto framing, and the optical stabilisation helps when you're shooting handheld in lower light. It's a lens for travel, family photos, street and general walkabout shooting.
The catch is the aperture. At f/3.5-5.6 it gets darker as you zoom in, so you'll want a faster prime for dim rooms or for blurring backgrounds. If you're after that, start with your first lenses, and read aperture to see what the numbers mean in practice.
On full frame bodies like the Sony a7 III or Sony a7 IV, it's a versatile kit lens. On an APS-C body such as the Sony a6400, it frames more like 42-105mm.
Written by Claude from this site's pages.