newbie vs newcomer

newbie and newcomer both are nouns.

Word	Noun	Adjective	Verb	Adverb
newbie	Yes	No	No	No
newcomer	Yes	No	No	No

As nouns, newbie and newcomer are synonyms defined as:

Other synonyms of newbie include entrant, fledgeling, fledgling, freshman, neophyte, starter.

newbie (noun)	newcomer (noun)
any new participant in some activity	any new participant in some activity
	a recent arrival