Is used in future contexts when talking about timetables, schedules, programmes and itineraries:agendas, horarios, programas e itinerarios.- Our flight to Dublin leaves tomorrow morning at 8.20 a.m.- What time does the play end? It ends at 11.30 p.m
Is used to talk about arrangements that you have made: Preparativos que hayas hecho.What are you doing on Saturday? I'm playing tennis with Jane.- Let's meet for a drink this afternoon- I'm finishing work early today.Note: Podemos usar "going to" para preparativos pero no suena natural.
"Going to"Is used to say what we intend to do in the future:Se usa cuándo tienes intención de hacer algo en el futuro.- We are going to watch tv tonight.
"Will"When a decision is made at the moment of speaking:- You've left the light on. Sorry, I'll turn it off.Is often used with "think":- I don't feel very well- I think I'll stay in this evening.- My brother thinks he'll quit his job next year.Is often used to make offers:If you're still hungry, I'll fix you a sandwich.Is used when promising:- I promise I'll bring you a souvenir from Thailand.