XML is a file format similar to Microsoft Word or an Adobe Acrobat file, a spreadsheet, or an online HTML page. However, it has different properties from them, namely:
• the XML standard is not controlled by a single organization; it is a standard 'open' to which anyone can contribute or use;
• from an ethnic point of view, XML files are not saved as 'binary' data but rather as plain text. This means that they are platform independent and can be read by people

• XML files do not have a specific structure, but use a set of basic (but strict) rules. Thus, XML files can represent many types of data and information from documents to files with images and financial transactions.
• XML rules can be used to restrict the structure of data types - so new standards can be created. The structure is of the self-descriptive type and each data is associated with a 'tag' to describe it in a way. This allows files to be validated by a computer, but even by people up to a certain level.
What is important is that, by defining strict rules but not imposing restrictions on the structure, 'standard XML' formats (called Schemas) can be developed to represent a particular type of data. There are "Standard XML schemas" for many types of information from business sales transactions to news formatting.
Although XML is a standard (ie there are rules for creating these files) problems can still occur, as such different and yet similar structures can be created using descriptions with XML schema. This was a big problem at first, but now organizations are starting to work together (many through the W3C) to develop and promote a single XML standard for each problem area.