A verb is an action word that indicates the thing that a person or object does or did while an adverb is used to modify a verb.
What a verb and adverb does
A verb is an action that is used to show something done. For instance, the statement., "The child goes to school" contains the verb, goes which connotes the act of moving to a place. Also, the adverb, suddenly is used to modify a verb by showing how an action was performed.
There are adverbs of place, time, condition, etc. The above adverb helps the reader imagine the way in which an act was performed, and that is, suddenly.