The simple future is used to express something that will happen in the future.
In English there are two common ways of expressing the future.
- With will. e.g. I will go to the store later
- With be going to. e.g. I am going to go to the store later.
In some cases either will or be going to can be used. If you are talking about predictions about the future, either will or be going to is possible.
If you have prior plans or intentions, then use be going to.
- E.g. You are talking to someone. You make a decision while you are talking to the person. You use Will.
- E.g. You are talking to someone. You made the decision before talking to the person. You use be going to.