loggerhead turtle vs sea turtle

loggerhead turtle and sea turtle both are nouns.

Word	Noun	Adjective	Verb	Adverb
loggerhead turtle	Yes	No	No	No
sea turtle	Yes	No	No	No

As nouns, sea turtle is a hypernym of loggerhead turtle; that is, sea turtle is a word with a broader meaning than loggerhead turtle:

loggerhead turtle: very large carnivorous sea turtle; wide-ranging in warm open seas
sea turtle: any of various large turtles with limbs modified into flippers; widely distributed in warm seas

Other hypernyms of loggerhead turtle include marine turtle.

loggerhead turtle (noun)	sea turtle (noun)
very large carnivorous sea turtle; wide-ranging in warm open seas	any of various large turtles with limbs modified into flippers; widely distributed in warm seas