a) Form

1.- "Will"

	Form		Contraction
I	Will		I'll
You	Will		You'll
He / she / it	Will		He'll / She'll / It'll
We	Will		We'll
You	Will		You'll
They	Will		They'll

2.- "Going to"

	Form		Contraction
I	am going to		I'm going to
You	are going to		You're going to
He / she / it	is going to		He's / She's / It's going to
We	are going to		We're going to
You	are going to		You're going to
They	are going to		They're going to

 

b) Use

1.- We use "will" when we make decision at the time of speaking. A decision that has not been decided before.

Katie: Let's go out for dinner

Maria: That's a good idea. We'll go to the Chinese restaurant.

2.- We use "going to" when we have already decided to do something.

(Maria and Katie have already decided to eat Chinese food)

Maria: Katie and I have decided to go out for dinner. We're going to eat Chinese.

James: That's nice.

Compare:

"Manuel is in London". "Oh really? I didn't know. I'll phone him later"

"Manuel is in London". "Yes, I know. I'm going to see him later"

3.- You use "will" or "going to" when you are predicting what will happen:

I think John will go to the party

I think John is going to go to the party

4.- You use "going to" when you use facts or events in the present situation as evidence for a prediction:

It's going to rain

Oh dear, I'm going to be late.

5.- You use "going to" when something is clearly going to happen very soon and as a warning:

Watch out, we're going to crash

Be careful, you are going to drop those glasses

6.- You use "will" when you are making a promise or an offer:

I'll ring you later tonight

I'll come round and help you later