foster care vs guardianship

foster care and guardianship both are nouns.

Word	Noun	Adjective	Verb	Adverb
foster care	Yes	No	No	No
guardianship	Yes	No	No	No

As nouns, guardianship is a hypernym of foster care; that is, guardianship is a word with a broader meaning than foster care:

foster care: supervised care for delinquent or neglected children usually in an institution or substitute home
guardianship: attention and management implying responsibility for safety

Other hypernyms of foster care include care, charge, tutelage.

foster care (noun)	guardianship (noun)
supervised care for delinquent or neglected children usually in an institution or substitute home	the responsibility of a guardian or keeper
	attention and management implying responsibility for safety