The Adverb:

An adverb is a word which adds something to the meaning, of a verb, an Adjective or another Adverb

Examples:

He runs fast. (Fast modifies run)

The boy seems very happy. (very modifies happy)

The poem was written very beautifully (very modifies beautifully)

He worked hard

Shah Jahan ruled very wisely

He is quite intelligent

In the sentence given above the Adverb modifies a verb.