The document discusses the use of different past tenses in English including:
1) The simple past is used to describe completed actions and states in the past. It can also be used to describe a series of completed actions.
2) The past continuous expresses an action that was interrupted by a shorter action in the simple past. It can also indicate a longer action occurring at a specific time.
3) The past perfect refers to actions that occurred before a specific past time or event.