idol vs simulacrum

idol and simulacrum both are nouns.

Word	Noun	Adjective	Verb	Adverb
idol	Yes	No	No	No
simulacrum	Yes	No	No	No

As nouns, simulacrum is a hypernym of idol; that is, simulacrum is a word with a broader meaning than idol:

idol: a material effigy that is worshipped
simulacrum: a representation of a person (especially in the form of sculpture)

Other hypernyms of idol include effigy, image.

idol (noun)	simulacrum (noun)
a material effigy that is worshipped	a representation of a person (especially in the form of sculpture)
an ideal instance; a perfect embodiment of a concept	an insubstantial or vague semblance
someone who is adored blindly and excessively