Can someone point out the part of documentation that specifies how the directory of a raco package for a language should be structured?

For example for a package abc: • what should go into the directory private ? • what role does main.rkt plays? • if you want to use #lang abc/xyz then you need to have directory named xyz and a lang directory with a reader.rkt inside containing the certain content I’m very confused as it seems I can’t such information documented anywhere but have to deduce them myself from inspecting other packages. If they are supposed to be deduced from first principles of the mechanisms of the module system and the package system, can someone also explain how to get there?

https://docs.racket-lang.org/guide/language-collection.html\|https://docs.racket-lang.org/guide/language-collection.html is a good introduction

But your questions seem to mostly be about module names

Those are mostly answered here: https://docs.racket-lang.org/guide/module-basics.html#%28part._link-collection%29\|https://docs.racket-lang.org/guide/module-basics.html#%28part._link-collection%29