philanderer vs Don Juan

philanderer and Don Juan both are nouns.

Word	Noun	Adjective	Verb	Adverb
philanderer	Yes	No	No	No
Don Juan	Yes	No	No	No

As nouns, Don Juan is a hyponym of philanderer; that is, Don Juan is a word with a more specific, narrower meaning than philanderer:

philanderer: a man who likes many women and has short sexual relationships with them
Don Juan: any successful womanizer (after the legendary profligate Spanish nobleman)

Other hyponyms of philanderer include Casanova, Lothario, masher, skirt chaser, wolf, woman chaser.

philanderer (noun)	Don Juan (noun)
a man who likes many women and has short sexual relationships with them	a legendary Spanish nobleman and philanderer who became the hero of many poems and plays and operas
	any successful womanizer (after the legendary profligate Spanish nobleman)