The document summarizes the functions of 16 tenses in English, organized into simple, continuous, perfect, and perfect continuous forms for present, past, and future times. It provides examples of when each tense is used, such as to describe habits, scheduled events, recent completion of an action, planned or predicted events, and relationships between actions that have occurred or will occur at different times. The tenses are used to focus on the time an action or event takes place or to emphasize its duration.