good vs better

good and better both are nouns.

Word	Noun	Adjective	Verb	Adverb
good	Yes	Yes	No	Yes
better	Yes	Yes	Yes	Yes

As nouns, better is a hyponym of good; that is, better is a word with a more specific, narrower meaning than good:

good (noun)	better (noun)
a raw material that is sold in large quantities, usually to other businesses for manufacturing or production purposes	something superior in quality or condition or effect
benefit	the superior one of two alternatives
moral excellence or admirableness	someone who bets
that which is pleasing or valuable or useful	a superior person having claim to precedence

good (adjective)	better (adjective)
having desirable or positive qualities especially those suitable for a thing specified	(comparative of `good') superior to another (of the same class or set or kind) in excellence or quality or desirability or suitability; more highly skilled than another
morally admirable	(comparative of `good') changed for the better in health or fitness
promoting or enhancing well-being	(comparative and superlative of `well') wiser or more advantageous and hence advisable
having the normally expected amount	more than half
with or in a close or intimate relationship
thorough
generally admired
resulting favorably
not left to spoil
not forged
tending to promote physical well-being; beneficial to health
in excellent physical condition
appealing to the mind
agreeable or pleasing
exerting force or influence
most suitable or right for a particular purpose
capable of pleasing
deserving of esteem and respect
of moral excellence
having or showing knowledge and skill and aptitude
financially safe

good (adverb)	better (adverb)
(often used as a combining form) in a good or proper or satisfactory manner or to a high standard (`good' is a nonstandard dialectal variant for `well')	comparative of `well'; in a better or more excellent manner or more advantageously or attractively or to a greater degree etc.
completely and absolutely (`good' is sometimes used informally for `thoroughly')	from a position of superiority or authority