Final answer:
An adjective modifies or describes a noun, while an adverb modifies a verb.
Step-by-step explanation:
An adjective modifies or describes a noun. For example, in the sentence 'I need to find an affordable car,' the adjective 'affordable' is modifying the noun 'car.'
An adverb acts as a modifier of a verb, describing its time, place, reason, or manner. For instance, in the sentence 'Pierre quickly ran through the main points of his argument,' the adverb 'quickly' is modifying the verb 'ran.'