A. An adverb tells more about a verb in the sentence.Example :
1. The fire engine runs fast.
2. Listen to his speech carefully.

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

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