Can you better explain the semantics of TestNG's @BeforeTest annotation?

Question

I read the relevant documentation and didn't understand it. See also this question.

Answer 1

To understand that, you must understand testng.xml. Now reread the same thing,

The annotated method will be run before any test method belonging to the classes inside the <test> tag is run.

It should be clear that this annotation will only work with the methods those belong to the classes defined under <test> tag in testng.xml.