Idiomatic future and simple future ( comparison)

Simple Future has two different forms in English: "will" and "be going to." Although the two forms can sometimes be used interchangeably, they often express two very different meanings. These different meanings might seem too abstract at first, but with time and practice, the differences will become clear. Both "will" and "be going to" refer to a specific time in the future.

• "Will" often suggests that a speaker will do something voluntarily. A voluntary action is one the speaker offers to do for someone else. Often, we use "will" to respond to someone else's complaint or request for help. We also use "will" when we request that someone help us or volunteer to do something for us. Similarly, we use "will not" or "won't" when we refuse to voluntarily do something.
• "Will" is usually used in promises.
• "Be going to" expresses that something is a plan. It expresses the idea that a person intends to do something in the future. It does not matter whether the plan is realistic or not.

Both "will" and "be going to" can express the idea of a general prediction about the future. Predictions are guesses about what might happen in the future. I