Adverbs modify verbs, adjectives, or other adverbs, and often tell us how, when, where, or to what extent something happens.
Examples:
* When did you arrive? (When is an adverb modifying the verb "arrive")
* He arrived early. (Early is an adverb modifying the verb "arrived")
* The movie was very scary. (Very is an adverb modifying the adjective "scary")