There's plenty of overlap and lots of gray areas, but here are some very general guidelines for talking about the future: Use the Simple Future for making predictions based on your thoughts or opinions, talking about things you've just decided to do or offering to help someone. Use the "going to" future to make predictions based on what you can easily see. Use the Present Continuous or the "going to" future to talk about plans or arrangements you've made for the future. Use the Simple Present to describe schedules and timetables.

Definetely, can you explain then?

It depends entirely on the context.