While adverbs primarily modify verbs, they can also modify adjectives and other adverbs. This is because adverbs often describe how, when, where, or to what extent something happens, and this information can apply to adjectives as well.
Here are some examples:
Modifying a verb:
* He quickly ran to the store. (modifies the verb "ran")
Modifying an adjective:
* The house was incredibly beautiful. (modifies the adjective "beautiful")
Modifying another adverb:
* He ran very quickly. (modifies the adverb "quickly")