Adjectives describe nouns and pronouns to make their meanings more clear or exact, while adverbs describe verbs, adjectives, and other adverbs. The key difference is that adjectives modify nouns and pronouns, while adverbs modify verbs, adjectives, and other adverbs. Examples are provided to illustrate adjectives describing nouns like "classical music" and adverbs describing verbs like "sing softly." Care must be taken to use adjectives and adverbs correctly in sentences.