alphanumerics vs character set

alphanumerics and character set both are nouns.

Word	Noun	Adjective	Verb	Adverb
alphanumerics	Yes	No	No	No
character set	Yes	No	No	No

As nouns, character set is a hypernym of alphanumerics; that is, character set is a word with a broader meaning than alphanumerics:

alphanumerics: a character set that includes letters and digits and punctuation
character set: an ordered list of characters that are used together in writing or printing

alphanumerics (noun)	character set (noun)
a character set that includes letters and digits and punctuation	an ordered list of characters that are used together in writing or printing