This document discusses verb tenses, specifically the past perfect and past perfect progressive tenses. It provides examples of how to form sentences using these tenses in statements, yes/no questions, short answers, and wh- questions. It also discusses time words and expressions that are commonly used with these tenses, such as "after", "before", "by the time", and "when". The purpose of these tenses is to indicate that one past action was completed before another past action occurred. The document provides exercises for readers to practice forming sentences using these tenses.