¿Qué es la diferencia? Voy a ir a España. I am going to Spain. Iré a España. I will go to Spain. In English it is kinda of clear. But still, what is the difference between you are going to do something and you will do something? The best explanation is that we use Ir+a+infinitive for the more immediate future (couple of days, a week, month, one year). Anything in the further future (more than a year, etc.) we use the true Future tense.