Adverbs usually modify a verb but can also modify adjectives or other adverbs. An adverb can be one word or a group of words called an adverbial phrase.
When modifying a verb, adverbs provide details about the action taking place, such as when it happened or how often it happens. An adverbial phrase, which doesn't have a subject or verb, serves the same function as an adverb. Prepositional and infinitive phrases can both act as adverbs. A conjunctive adverb links clauses or sentences together. Adverbs are often intensifiers, meaning they either emphasize, amplify or tone down what they modify. Adverbs are known for their flexibility regarding placement in a sentence.