Mogen David vs emblem

Mogen David and emblem both are nouns.

Word	Noun	Adjective	Verb	Adverb
Mogen David	Yes	No	No	No
emblem	Yes	No	No	No

As nouns, emblem is a hypernym of Mogen David; that is, emblem is a word with a broader meaning than Mogen David:

Mogen David: a six-pointed star formed from two equilateral triangles; an emblem symbolizing Judaism
emblem: a visible symbol representing an abstract idea

Other hypernyms of Mogen David include allegory, hexagram.

Mogen David (noun)	emblem (noun)
a six-pointed star formed from two equilateral triangles; an emblem symbolizing Judaism	special design or visual object representing a quality, type, group, etc.
	a visible symbol representing an abstract idea