[rochachat]

Hi Beth

I would give you an example. You can use "I'm going to" when you have something planned. e.g. I'm going to France next month, or I'm going to retire in three months time... etc.
However you can use "will" when you dicide to do something NOW or you take a decision NOW... you didn't have time to 'plan'.
e.g.
Mum: John I'm busy now could you or Tom go to the shop?

Tom: Ok mum, I'll (I will) do that.

Tom in the example had no time to 'plan' to go to the shop, he dicided to go 'now' just before his mum had asked one of them (Tom or John) to go...

I'm going to = used when you have planned (or have been planning) during some time ...
Will = used when you had no time to plan (Or when you dicided/ or take a decision NOW).

GOOD LUCK
lUCY