The way we name EXTRA_ANSWER_IS_TRUE

Android Programming (3rd Edition) 5. Your Second Activity
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EXTRA_ANSWER_IS_TRUE = “com…geoquiz.answer_is_true”;
why we put package there…
i don’t really understant the explain in the book.
i hope someone can give a example to that i can understant…
thank you … my English is not well as you see.