black pepper vs true pepper

black pepper and true pepper both are nouns.

Word	Noun	Adjective	Verb	Adverb
black pepper	Yes	No	No	No
true pepper	Yes	No	No	No

As nouns, true pepper is a hypernym of black pepper; that is, true pepper is a word with a broader meaning than black pepper:

black pepper: climber having dark red berries (peppercorns) when fully ripe; southern India and Sri Lanka; naturalized in northern Burma and Assam
true pepper: any of various shrubby vines of the genus Piper

Other hypernyms of black pepper include pepper vine.

black pepper (noun)	true pepper (noun)
pepper that is ground from whole peppercorns with husks on	any of various shrubby vines of the genus Piper
climber having dark red berries (peppercorns) when fully ripe; southern India and Sri Lanka; naturalized in northern Burma and Assam