:logger IIRC starts “automatically” only in development (and in production it will start due to fact that this is commonly present in deps). However there are other applications that can be present in application and aren’t started by default, :inet is one of them (it is automatically started in Phoenix as one of it’s deps include that app).
About :mod it say which is the “launching point” module in our application. Otherwise how would :init supervisor know where is the main launching point of our application? There is no “convention” there.
