WILL and GOING TO: future tense

Phrase used when something is about to happen
He's going to
Look at Andrey! He's going to jump off the diving board!
Phrase used when there are definite signs that something will happen
it's going to
It's going to storm soon. The sky has darkened and the wind is blowing.
Phrase used to talk about intentions
we're going to
Once everyone in our group arrives we're going to eat out at our favorite restaurant.
Verb used to make predictions based on thoughts or beliefs
will
I think Morris will do well on his exams.
Verb used to make instant decisions
I'll
"Hey there's Sacha! I'll go over there and say hello."
Verb used to make a promise
will
I will always love you.
Verb used to make offers
will
You guys go walk around. We will set up the tent.
Verb to be [future]
will
There will be a full moon tomorrow night.