sheep dog vs briard

sheep dog and briard both are nouns.

Word	Noun	Adjective	Verb	Adverb
sheep dog	Yes	No	No	No
briard	Yes	No	No	No

As nouns, briard is a hyponym of sheep dog; that is, briard is a word with a more specific, narrower meaning than sheep dog:

sheep dog: any of various usually long-haired breeds of dog reared to herd and guard sheep
briard: old French breed of large strong usually black dogs having a long tail and long wavy and slightly stiff coat

sheep dog (noun)	briard (noun)
any of various usually long-haired breeds of dog reared to herd and guard sheep	old French breed of large strong usually black dogs having a long tail and long wavy and slightly stiff coat