An adverb is a word that modifies a verb, an adjective, or another adverb. It answers one of five questions about the word or phrase that it modifies:
1. How or in what manner?
4. How often?
5. To what extent or degree?
1) The owl hooted loudly. (How did the owl hoot? Loudly.)
2) My date arrived early. (When did my date arrive? Early.)
3) My father rarely watches television. (How often does my father watch television? Rarely.)
4) As a rule, people find philosophy completely fascinating. (People find philosophy fascinating to what extent? Completely.)
5) The star is too distant to be seen with that telescope. (Too tells the degree of distance to the star.)
6) The sun looks much larger near the horizon. (Much tells to what extent the sun looks larger.)
7) Earth moves rather quickly through the heavens. (Rather tells to what extent Earth moves quickly.)
8) Astronomers understand the behavior of the atmosphere quite well. (Quite tells to what extent astronomers understand the behavior of the atmosphere.)
The words not and never are adverbs that tell to what extent (not at all) and when (not ever).
1. The last lunar eclipse did not impress me. (Not modifies the verb phrase did impress.)
2. Scientists will never completely understand the mysteries of the universe. (Never modifiers the verb phrase will understand and so does the adverb, completely.)