Following points define to where use XML:
1.XML is portable and non-proprietary, Information identification because you can define your own markup; you can define meaningful names for all your information items. Information storage, it can be used to store textual information across any platform. Because it is backed by an international standard, it will remain accessible and process able as a data format.
2.XML has been designed for ease of implementation and for interoperability with both SGML and HTML. Despite early attempts, browsers never allowed other SGML, only HTML, and they allowed it to be corrupted or broken, which held development back for over a decade by making it impossible to program for it reliably.
3. XML fixes that by making it compulsory to stick to the rules, and by making the rules much simpler than SGML. But XML is not just for Web pages: in fact its very rarely used for Web pages on its own because browsers still dont provide reliable support for formatting and transforming it.
4. Combining these three topics (identity, storage, structure) means it is possible to get all the benefits of robust document management and control (with XML) and publish to the Web (as HTML) as well as to paper (as PDF) and to other formats (eg Braille, Audio, etc) from a single source document by using the appropriate stylesheets.