
Contrary to what I had thought, but according to Wikipedia, philately is not stamp collecting, but is the study of stamps. Taking that fact into consideration, someone could be a stamp collector, but not a philatelist. On the other hand, someone might be a philatelist, but not a stamp collector. However, one who has a large extensive stamp collection may desire and need some philatelic knowledge.
It was interesting to me also to learn that some smaller countries create limited runs of elaborate stamps to be bought by stamp collectors. These collectible stamps have become an important source of revenue for these countries.