This is a screenshot of the brake booster (left column part number) and the master cylinder (right column part number).

What does the STAR mean? What does "m/w" mean? What does "r/b" mean?

 

Black star means that part isn't offered as an over the counter replacement part. "r/b" means replaced by. I'll have to look into what m/w means.
EDIT:
The catalog doesn't show "m/w" in the list of abreviations in the catalog's index. From the way it's used I would say it's interchangeable with "r/b".
Just my 2 cents.

 

M/W is not listed in the list of abbreviations in the beginning of the catalog. my guess it means Maximum Weight ?
See here for Power Brake Booster.