What is an adverb for?

It is used to modify verbs, adjectives, and other adverbs.

For example: He runs quickly.

She is really unhappy.

He plays piano very well.

It is used to modify an entire clause.

For example: Perhaps he will come after the interview, but I cannot wait any longer.

It is used to modify all the rest of a sentence.

For example: Perhaps he will come after the interview.