overlayer vs protective cover

overlayer and protective cover both are nouns.

Word	Noun	Adjective	Verb	Adverb
overlayer	Yes	No	No	No
protective cover	Yes	No	No	No

As nouns, protective cover is a hypernym of overlayer; that is, protective cover is a word with a broader meaning than overlayer:

overlayer: protective covering consisting, for example, of a layer of boards applied to the studs and joists of a building to strengthen it and serve as a foundation for a weatherproof exterior
protective cover: a covering that is intend to protect from damage or injury

Other hypernyms of overlayer include protection, protective covering.

overlayer (noun)	protective cover (noun)
protective covering consisting, for example, of a layer of boards applied to the studs and joists of a building to strengthen it and serve as a foundation for a weatherproof exterior	a covering that is intend to protect from damage or injury