1、am/ is/ are going to + do和will/ shall do.
Which paragraph shall I read first?
2、be going to+动词原形或地点，表将来
What are you going to do tomorrow?（明天你将要做什么？）
Look at the dark clouds, there's going to be a storm.
3、be+不定式表将来，表按计划或正式安排将发生的事。
We are to discuss the report next Saturday.