Modifying the Verb
The word adverb literally means “something that is added to the verb” (in Latin ad = to and verbum = word, verb). It’s not surprising, then, that adverbs often modify verbs:
Jennifer bugged Mike relentlessly.
If we ask bugged how? the answer would be relentlessly.
Even prepositional phrases can act like an adverb and modify the verb:
I saw you through the window.
Here the prepositional phrase through the window tells us where I saw you. Prepositional phrases always act like adjectives or adverbs, so context is everything.