philately vs stamp collecting

philately and stamp collecting both are nouns.

Word	Noun	Adjective	Verb	Adverb
philately	Yes	No	No	No
stamp collecting	Yes	No	No	No

As nouns, philately and stamp collecting are synonyms defined as:

philately and stamp collecting: the collection and study of postage stamps

Other synonyms of philately include stamp collection.

philately (noun)	stamp collecting (noun)
the collection and study of postage stamps	the collection and study of postage stamps