The document defines and provides characteristics of the past simple tense in English grammar. It notes that the past simple tense is used to describe actions that were completed in the past, often accompanied by a temporal expression like "yesterday." It lists characteristics like the main verb is in the past tense and it uses verbs in their past form. Examples are provided for regular and irregular verb conjugations in the past simple tense, as well as examples of negative and positive statements and question forms.