Adverbs modify a verb, an adjective, or another adverb.

A. An adverb tells more about a verb in the sentence. Example:
The fire engine runs fast.
It rained hard.

B. An adverb describes more about an adjective in the sentence.Example:
The news is very surprising!
Nature is really amazing!

C. An adverb modifies another adverb in the sentence.Example:
It rains very hard.
Computers run much faster these days.