The document discusses the past simple tense in English. It defines the past simple as expressing completed actions in a time before now. Examples are given of regular verbs formed by adding "-ed" and irregular verbs that change form. The past simple is used to refer to specific times in the past using time expressions like "yesterday" or "last year." It can also refer to unspecified times like "a long time ago." Questions are formed by using "did" plus the infinitive verb form, and negatives by using "didn't" plus the infinitive.