foster parent vs protector

foster parent and protector both are nouns.

Word	Noun	Adjective	Verb	Adverb
foster parent	Yes	No	No	No
protector	Yes	No	No	No

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

foster parent: a person who acts as parent and guardian for a child in place of the child's natural parents but without legally adopting the child
protector: a person who cares for persons or property

Other hypernyms of foster parent include defender, guardian, shielder.

foster parent (noun)	protector (noun)
a person who acts as parent and guardian for a child in place of the child's natural parents but without legally adopting the child	a person who cares for persons or property