The document discusses the simple future tense in English. It explains that there are two forms: "will" and "be going to." While sometimes interchangeable, they often express different meanings. "Will" is used to express voluntary actions, promises, and predictions. "Be going to" expresses plans and can also be used for predictions. The simple future tense follows a subject + auxiliary verb + main verb structure. Examples are provided to illustrate the different uses and forms of the simple future tense.