What is __main__ ??

Answer 1

Before programs are executed, special variables are defined. Take into account, you're running your program from a source file and that source file is like your main program. A special variable that's called __name__ will have the value of '__main__'. If you're importing the module to like another module __name__ will have the value of the module's name instead of '__main__'.
All in all, it's not too hard of a concept. If you're confused I would strongly recommend for you to search it up. You might learn something new.

Answer 2

It seems to be one of those "too simple" situations. Let me see if I understand this - please correct me if I'm wrong:
There is a default __name__ that has the value "__main__". This default is only changed, behind the scenes, when the code includes an import command, in which case the value of __name__ becomes that of the imported command. So if my understanding is correct, then this code below will print "__main__" and "re" on two lines:
print(__name__)
import re
print(__name__)
But it doesn't: it prints "__main__" twice. Likewise if I change import re to from sys import argv. I still get "__main__" printed twice.
What am I missing?
PS I'm the guy who finds the iPhone too simple to be user-friendly and struggle with it.