What is an adverb? You have more than likely heard about the adverb, but what is its purpose within English grammar? In this article, we are going to find out exactly what an adverb is as well as how it can be used within a sentence. We are going to look at a variety of examples of adverbs being used as a way to further gain an understanding of their function. Learn adverb definition, different adverb types and useful grammar rules to use adverbs in sentences with ESL printable worksheets and example sentences.