This document provides information about and examples of using the past perfect and past simple tenses in English. It explains that the past perfect tense is used to talk about something that happened before another action in the past. It also indicates that the past perfect tense cannot be used with specific time expressions like "yesterday" or "at 5pm", which require using the past simple instead. Examples are given showing a situation expressed with the past perfect tense and another with the past simple to illustrate the difference.