The document discusses different types of past tense grammar in English:
1) Past Simple is used to talk about completed actions in the past and habitual actions. It is formed by adding "-ed" to regular verbs or using the past form of irregular verbs.
2) Past Continuous describes actions that were ongoing at a specific time in the past. It is formed using "was/were" and the "-ing" form of the verb.
3) Past Perfect refers to actions that occurred before something else in the past. It is formed using "had" plus the past participle of the verb. It is used with time expressions like "before" or "by the time".