1) The document discusses various perfect tenses in English including the present perfect, past perfect, and present perfect continuous. 2) The present perfect describes an action that began in the past and continues in the present. The past perfect describes an action that occurred before another past action. 3) The present perfect continuous is used for actions that began in the past and continue up to the present, and may or may not have finished. It compares the present perfect and present perfect continuous tenses.