The grammar box provides rules for using 'will' for future simple.
I/you/he/etc will swim.
I/you/he/etc won't swim. (will not = won't)
Will I/you/he/etc swim?
Yes, I/you/he/etc will.
No, I/you/he/etc won't.
Note: 'be going to' is used for plans. For example: 'What are you going to do?' 'We are going to go swimming.'
Answer: The grammar box explains the formation and usage of the Future Simple tense with 'will' for on-the-spot decisions, requests, and predictions.