This tense is used:
1. When we say predictions about the future usually with the verbs believe, expect, think, etc.
My mum thinks that I will become a doctor one day.
2. When we make on-the-spot decisions and offers.
Since it's your birthday, I will pay for dinner.
3. When we say about the actions/situations which will definitely happen in the future and which we cannot control.
Kate will be three years old next month.
We use the future simple when we make a prediction based on what we imagine, think.
In the year 2060 there will be colonies on Mars.
Verb forms in different types of  sentences.
Positive Subject + will + V1
NegativeSubject + will + not + V1
QuestionsWill + subject + V1?
We will prepare documents soon.
He will not go to Moscow tomorrow.
Will you have a meeting next year?