Sometimes there really is a STUPID QUESTION and I have one

[Phyllis Smith]

Flatpak sounds like a great solution for the user.  But after reading a lot about it on the internet and in wiki, I do have a stupid question.  Doesn't the developer still have to create an executable for each of the operating systems? I am assuming that what I call the "executable" is the "runtime" that discussions refer to?  If not, then when the user installs the flatpak application is the compile performed on their computer?  Thank you for a response.   
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