The document discusses the simple past tense in Spanish. It is used to talk about completed actions or events that happened at a specific time in the past. It provides examples of affirmative sentences using the simple past tense with time expressions like "last year" and "when they were young." Negative sentences are formed with "didn't" and the infinitive verb form. Interrogative sentences asking about past events are formed with "did" and the subject and infinitive verb.