We can talk about future plans and events in English in many different ways. For example, we could just use the present simple:
My train leaves at 8:30 tomorrow
Here, we are speaking about a future event using the present. We need to indicate the time, of course. We can also use the present continuous for arrangements and appointments:
I am meeting Maria tomorrow.
She is playing football Thursday evening, so she cannot meet you.
We also need to use a time expression, generally. Sometimes we will use it without a time expression when it’s something that is about to happen:
(the bell rings) “I’m coming!”
Another option is using going to. We use this option generally when we have decided to do something, even if we have not arranged it or made an appointment. We can also use it in past to express you had plans for something that didn’t happen in the end.
I am going to study law from now on.
We are going to buy a new car.
She was going to take the exam yesterday, but she had an accident.
Going to is also used for predictions, when they are based on evidence we can see.
(we see some very dark clouds above the city) “It is going to rain a lot!”
Another way of talking about the future is using will. Will is used when we make a spontaneous decision:
Is Jessica coming? Then I’ll go too!
Will is also used when offering something, when you are agreeing or promising to do something, or when you are asking someone to do something.
That exercise is really difficult. I’ll help you a bit.
I’ll give you the book this Friday.
Will you please shut the door?
It is important to remember not to use will for arrangements or schedules.
Emma will work next week.
Emma is working next week
Finally, we can also use will for predictions, like going to. The difference is how sure we are of the prediction we are making:
It’ll rain next week.