Auxiliary verbs, also known as helping verbs, are used alongside main verbs to form different tenses, moods, or voices. Common auxiliary verbs include be, have, and do. For example, in the sentence "She is running," the verb "is" helps to indicate the present continuous tense. These verbs can also help to create questions and negatives. For instance, in the question "Do you like ice cream?" the word "do" is the auxiliary verb that assists the main verb "like." Understanding auxiliary verbs is essential for constructing clear and grammatically correct sentences.