The speaker's intention or the context of the comment helps to understand the use of the different tenses.
Examples:
- Hurry up! The show starts in five minutes. (shceduled event)
- I can't go with you tomorrow. I'm meeting my friend Patrick. (arrangement)
- Look at that car! It's going to crash! (prediction based on present evidence)
- I'm going to travel to Egypt this summer. I was in doubt first but I've decided to do it. (plan/intention)
- I believe people's ecological awareness will increase in the near future. (prediction)
- Mary says she'll bring her computer so we're OK in that area. (promise)
The following links take you to websites that offer more information on this topic:
British Council - future tenses
FIS - Future tenses
Follow this link to take a quiz to practise future tenses:
E-nglish Online - Future tenses quiz