There are two different forms in English to express future in the Simple Future: ' be going to' and 'will '. 'Will' is used to express promises and things we decide to do in the moment of speaking, 'going to' is used to express our plans. Both of those forms can be used to express our predictions. Here goes a list to make it more readable.
Use (Will) :
1. Promises (Use 1)
2. Unplanned actions (Use 2)
3. Predictions (Use 3)
Use (Going to)*:
1. Planned actions (Use 4) -- like in the Present Continuous 2. Prediction (Use 3)
The difference between them may sometimes seem not very clear but once you have read a few English books, you won't have any problems with this tense. *Sometimes you may encounter the form 'gonna', which is an abbreviation of 'going to'. 'Gonna' is rather informal so be careful while using it!
You will regret it (Use 2)
When I'm 60 years old, I will have a long beard (Use 2)
I will go to Mary (Use 1)
(the speaker decided to go to Mary in the moment of speaking.) Will he be angry when he sees me? (Use 2).
What do you think - will Mark arrive at 10 or 9? (Use 4)
I won't take any equipment with me (Use 1).
Mmmm... you know what? I won't be able to help you with your English today (Use 2) (The speaker didn't know you woudn't be able to help his or her friend with English - that's why it's 'Use 2'.) This team is definitely going to win the competition. (Use 3). I'm going to visit my grandma next week (Use 4).
Is The Government is not going to lower the taxes (Use 4 or Use 3). he going to apologise to Mary for his behavior? (Use 4).
We use the Future Continous to indicate that we will be in the middle of doing something in a specified time in the future. Use:
Incomplete actions in the future.
Tommorow at nine I will be hosing off (=washing with a hose) my car.
I am going to (=will) be watching TV when my mother arrives. Tommorow at this time, I will be getting...