When you´re sure about what you´re doing, when everything is set and clear, you use the PRESENT CONTINUOUS to talk about your so sure plans. Let´s go for the examples:
- I am meeting some friends after work.
- I am not going to the party tonight.
- Is he visiting his parents next weekend?
- Is he going to visit his parents next weekend? ( be going to is also present continous!)
- Isn't he coming with us tonight.