reminder vs message

reminder and message both are nouns.

Word	Noun	Adjective	Verb	Adverb
reminder	Yes	No	No	No
message	Yes	No	Yes	No

As nouns, message is a hypernym of reminder; that is, message is a word with a broader meaning than reminder:

Other hypernyms of reminder include content, subject matter, substance.

reminder (noun)	message (noun)
an experience that causes you to remember something	content communicating a message; what something is about
a message that helps you remember something	a communication (usually brief) that is written or spoken or signaled
someone who gives a warning so that a mistake can be avoided