Answer:
Adjectives are words that modify (describe) nouns.
Adverbs are words that modify (describe) verbs, adjectives, or other adverbs.
Examples:
The car is slow. (adjective slow describes car)
The car moves slowly. (adverb slowly describes moves)
The car is very slow. (adverb very describes adjective slow)
The car was driving very slowly. (adverb very describes adverb slowly)
Note that the antonym "fast" is both an adjective and an adverb.