This book has one aim. That is, to help students understand the various "past tenses" used in English. If you are struggling to grasp those tenses then this book will come in useful. Many of my students have faced great difficulties in trying to distinguish the past progressive from the past perfect progressive. One way to remember which is which is, that when we use the past progressive, we refer to an action in progress at a specific time point in the past. With the past perfect progressive we refer to an action in progress which started before a specific time point in the past and lasted up to that specific time point (when used with 'for' and 'since') or just before that specific time point when used without 'for' and 'since'. The past progressive or continuous as it is often referred as, does not refer to anything in progress before the specific past moment. Example: When I arrived, he was waiting. The progressive action of "waiting" refers to that specific moment and not before that moment I arrived. When I arrived, he had been waiting for an hour. The waiting was progressive also before I arrived and up to the moment I arrived. The book starts off with simple past tenses and progresses to more complex ones. More advanced "pasts" are illustrated toward the end of the book. Easily accessible answers follow each exercise.