The document discusses verb tenses in English. It describes how tenses can be classified based on time frame (present, past, future) or aspect (simple, continuous, perfect, perfect continuous). There are 12 possible tenses formed from combining these classifications. The document provides definitions and examples of each tense, such as using the present continuous to emphasize ongoing actions and the past perfect to refer to completed actions in the past. Rules for forming the different tenses are also outlined.