postiche vs Afro-wig

postiche and Afro-wig both are nouns.

Word	Noun	Adjective	Verb	Adverb
postiche	Yes	No	No	No
Afro-wig	Yes	No	No	No

As nouns, Afro-wig is a hyponym of postiche; that is, Afro-wig is a word with a more specific, narrower meaning than postiche:

postiche: a covering or bunch of human or artificial hair used for disguise or adornment
Afro-wig: a wig that gives the appearance of an Afro hairdo

Other hyponyms of postiche include switch, toupe, toupee, wig.

postiche (noun)	Afro-wig (noun)
something that is a counterfeit; not what it seems to be	a wig that gives the appearance of an Afro hairdo
a covering or bunch of human or artificial hair used for disguise or adornment