Admiralty Islands vs archipelago

Admiralty Islands and archipelago both are nouns.

Word	Noun	Adjective	Verb	Adverb
Admiralty Islands	Yes	No	No	No
archipelago	Yes	No	No	No

Admiralty Islands (noun)	archipelago (noun)
a group of islands in the Bismarck Archipelago	a group of many islands in a large body of water