XML stands for the Extensible Markup Language. It is a markup language for documents, much like HTML.
However, XML differs from HTML because it is extensible, meaning that users can define their own tags or other structural aspects of the document.
XML allows users to specify the type or form of a document, the elements of a document, the values of those elements, and the relationship of the document and elements to other documents and elements.
It’s important to remember that XML does not display data in web browsers
Although XML does share many similarities with HTML, a very important difference between these languages is that XML was not designed to describe page layout or functionality in the same way that HTML was. One way to understand this is to remember that XML does not create or modify the appearance of a web document – instead, it can be used to store data within a document.
XML is a tool to develop, store and share data. XML can communicate structured
information to other users. In other words, if a group of users agree to
implement the same kinds of tags to describe a certain kind of information,
XML applications can assist these users in communicating their information
in an more robust and efficient manner. XML can make it easier to exchange
information between cooperating entities.