An adverb is a word that modifies a verb, adjective, or another adverb. It typically expresses manner, place, time, degree, or frequency. In the sentence "She ran quickly to the store," the word "quickly" is an adverb that modifies the verb "ran." It tells us how she ran. On the other hand, a verb adjective is a verb that can also be used as an adjective. For example, the word "run" can be used as a verb (as in "She ran to the store") or as an adjective (as in "She is a good runner").