first team vs team

first team and team both are nouns.

Word	Noun	Adjective	Verb	Adverb
first team	Yes	No	No	No
team	Yes	No	Yes	No

As nouns, team is a hypernym of first team; that is, team is a word with a broader meaning than first team:

Other hypernyms of first team include squad.

first team (noun)	team (noun)
a team representing a college or university	a cooperative unit (especially in sports)
	two or more draft animals that work together to pull something

first team (verb)	team (verb)
	form a team