Bismarck Archipelago vs archipelago

Bismarck Archipelago and archipelago both are nouns.

Word	Noun	Adjective	Verb	Adverb
Bismarck Archipelago	Yes	No	No	No
archipelago	Yes	No	No	No

Bismarck Archipelago (noun)	archipelago (noun)
a group of islands in the southwestern Pacific to the northeast of New Guinea; part of Papua New Guinea	a group of many islands in a large body of water