An adverbial is a word or group of words that modifies a verb, an adjective, or another adverb, providing additional information about how, when, where, or to what extent something happens. Common types of adverbials include adverbs, prepositional phrases, and clauses. For example, in the sentence "She runs quickly," the word "quickly" is an adverbial that describes how she runs. Adverbials can enhance sentences by adding detail and clarity. They can indicate time, such as in "He will arrive tomorrow," or place, as in "They are playing outside." Understanding adverbials helps improve writing by making it more descriptive and engaging.