Here's why:
* Verbs describe actions or states of being (e.g., run, sleep, think).
* Adverbs modify verbs, adjectives, or other adverbs, providing more information about how, when, where, or to what extent something happens (e.g., quickly, happily, very, extremely).
In the sentence "He walked hurriedly to the store," "hurriedly" describes how he walked, modifying the verb "walked".