male horse vs Equus caballus

male horse and Equus caballus both are nouns.

Word	Noun	Adjective	Verb	Adverb
male horse	Yes	No	No	No
Equus caballus	Yes	No	No	No

As nouns, Equus caballus is a hypernym of male horse; that is, Equus caballus is a word with a broader meaning than male horse:

male horse: the male of species Equus caballus
Equus caballus: solid-hoofed herbivorous quadruped domesticated since prehistoric times

Other hypernyms of male horse include male, horse.

male horse (noun)	Equus caballus (noun)
the male of species Equus caballus	solid-hoofed herbivorous quadruped domesticated since prehistoric times