The document discusses past future tense and simple future tense in English. Past future tense refers to actions that were planned or predicted in the past from the past perspective, and is formed using "would" or "was/were going to". Simple future tense refers to actions that will occur in the future, and is formed using "will" or "be going to". Both tenses are used to make predictions, plans and promises. Examples are provided to illustrate the formation and use of past future tense and simple future tense.