What is ir+a+infinitive used for ?
ir+a+infinitive
5 Answers
The 1st personal, plural formation has to be examined in context because vamos a + verb infiinitive can mean the near future the same as the other persons of the Ir verb conjugation, but it is also the same construction as one method of forming nosotros commands.
vamos a hablar=we are going to talk (near future)
vamos a hablar= let's talk (hablemos...nosotros command)
Basically it's often used as a substitute for the future tense in Spanish. (Technically I think called the Periphrastic Future but you probably won't worry about knowing that lol)
This explanation may help 
Ir + a + inf
I think it's easiest to understand this usage when you've conjugated the verb "ir" to suit the person or people you're talking about. To build on Kiwi Girl's explanation, I'll give a couple examples:
Voy a comer - I am going to eat; Vas a pensar - You are going to think; Van a aprender - They are going to learn.
The ir+a+infinitive form allows us to talk about what is "going to" happen in the future.
-Mateo
I'm a little late to the party, but I thought I'd throw this in.
My first Spanish teacher told me that "ir + a + infinitive" is the "gunna" phrase. Obviously, "gunna" isn't proper English, but that is what she called it because that is how native English speakers often say "going to".
Any conjugated form of ir + the preposition a + any infinitive
Vamos + a + hablar + con + Pablo = We are going to talk with Pablo...We are gunna talk with Pablo.
"Ir + a + infinitive" is a way of expressing the future (it is the informal future).
Parece que va a llover.
Vas a venir?
El año que entra voy a Europa.
