XML stands for Extensible Markup Language. It is a text based way of storing and transferring data in a very organised, structured and readable way.
It was created as a way of standardising the way raw data can be transferred over the web. Transferring data can be done in any number of ways, but a common language was needed so that applications and programs could easily read data from any number of sources.
XML files can be opened in any text editor and read by a computer or humans. Mostly however a computer will convert the data into a more aesthetic and readable format for viewing as it is still just a lot of text.
The following example shows how book data might be used in an XML file:
<book> <title>Nineteen Eighty-Four</title> <author> George Orwell</author > <published>1949</published> <genre>Social Science Fiction</genre > </book>
It stores the data inside tagged angle brackets. The first book tag tells us that we are about to get the data relating to a book. Then after the book tag we are given the title, author, published date and genre. Note how the tags end using the forward slash “/”. This makes the data both readable to us and also very readable to a computer.
Once the book tag has closed using the </book> tag another one can start. This way we can transfer a whole library of book related data in a single XML file.