An adverb is a word that tells us more about a verb. It "qualifies" or "modifies" a verb (The man ran quickly). Examples:.

1. John speaks loudly. (How does John speak?)
2. Afterwards she smoked a cigarette. (When did she smoke?)
3. Mary lives locally. (Where does Mary live?)

But adverbs can also modify adjectives (Tara is really beautiful), or even other adverbs (It works very well). Look at these examples:
A. Modify an adjective:
- He is really handsome. (How handsome is he?)
- That was extremely kind of you.

B. Modify another adverb:
- She drives incredibly slowly. (How slowly does she drive?)
- He drives extremely fast.