You asked
What is the olympus m zuiko 45mm f 1 8 good for?
The Olympus M.Zuiko 45mm f/1.8 is a small, cheap portrait lens. On Micro Four Thirds it frames like a 90mm on full frame, a comfortable distance for headshots and tight portraits. At f/1.8 it gives about the depth of field of f/3.6 there, so backgrounds soften nicely. It isn't stabilised, so keep your shutter speed up for handheld shots.
If you want to pair it with a body, these fit it:
For more on choosing a focal length for people, see the portraits guide.
Written by Claude from this site's pages.