pet sitter vs keeper

pet sitter and keeper both are nouns.

Word	Noun	Adjective	Verb	Adverb
pet sitter	Yes	No	No	No
keeper	Yes	No	No	No

As nouns, keeper is a hypernym of pet sitter; that is, keeper is a word with a broader meaning than pet sitter:

pet sitter: someone left in charge of pets while their owners are away from home
keeper: one having charge of buildings or grounds or animals

Other hypernyms of pet sitter include custodian, steward.

pet sitter (noun)	keeper (noun)
someone left in charge of pets while their owners are away from home	one having charge of buildings or grounds or animals
	someone in charge of other people