It is important to understand that XML was designed to store, carry, and exchange data. XML was not designed to display data.
XML can Separate Data from HTML
With XML, your data is stored outside your HTML.
When HTML is used to display data, the data is stored inside your HTML.With XML, data can be stored in separate XML files. This way you can concentrate on using HTML for data layout and display, and be sure that changes in the underlying data will not require any changes to your HTML.
XML data can also be stored inside HTML pages as "Data Islands".
XML is Used to Exchange Data
With XML, data can be exchanged between incompatible systems.
In the real world, computer systems and databases contain data in incompatible formats. One of the most time-consuming challenges for developers has been to exchange data between such systems over the Internet.
Converting the data to XML can greatly reduce this complexity and create data that can be read by many different types of applications.
XML Can be Used to Share Data
With XML, plain text files can be used to share data.
Since XML data is stored in plain text format, XML provides a software- and hardware-independent way of sharing data.
This makes it much easier to create data that different applications can work with. It also makes it easier to expand or upgrade a system to new operating systems, servers, applications, and new browsers.