XML stands for Extensible Markup Language. XML is designed to describe data. XML tags are not predefined, you can define your own tags.
XML is actually a meta languague - a language for describing other languages - which lets you design your own markup languages.
XML is sometimes referred to as 'self-describing data' because the names of the markup elements should represent the type of content they hold.
XML Document example
Common Uses of XML
1. Information Identification
Since you can define your own markup, you can define meaningful names for all your information.
2. Information storage
XML can be used to store textual information across any platform.
3. Information structure
XML can be used to store and identify any kind of (hierarchical) information structure especially for long, deep, or complex document sets or data sources, making it ideal for information management back-end to serving the Web.
XML has the benefits of robut document management and control (with XML) and publish to the Wen (as HTML) as well as to paper (as PDF) and to other formats (eg., Braille, Audio, etc) from a single source document by using hte appropriate stylesheets.
5. Messaging and Data Transfer
XML is very heavily used for enclosing or encapsulating information in order to pass it between different computing system.
6. Web Services
Because of its use in browsers, machine processable data can be exchanged between consenting system. Weather services, e-commerce sites, AJaX sites and thousands of other data-exchange services use XML for data management and transmission.
Companies are discovering that by communicating via the Internet, instead of by more traditional methods (such as faxing, human-to-human communication, and so on) they can streamline their processes, decreasing costs and increasing response times. Whenever one company needs to send data to another, XML is the perfect format for exchange.
8. Distributed Computing
XML can be used as a means for sending data for distributed computing, where objects on one computer call objects on another computer to do work. There have been numerous standards for distributed computing such as DCOM, CORBA, and RMI/IIOP, but as using XML and HTML through web services and/or SOAP enables this to occur even through a firewall.