This document discusses "to be" verbs and their uses in linking verbs, progressive and perfect verb tenses, and passive voice constructions. "To be" verbs like is, are, was, were can link subjects to complements in sentences or act as auxiliary verbs to form progressive and perfect verb tenses. The passive voice places emphasis on the object of an action rather than the subject and is sometimes used when the actor is unknown, irrelevant, or to be vague or emphasize the recipient of the action.