Standard of data exchange between different programs and systems
is the XML language. or "Extensible Markup Language".
It is generally similar to the "HTML".
Similarly, you can create hierarchical tree structure.
Each data element starts with a opening and ends with a closing tag.
Between the opening and closing tags are child elements.
While the "HTML" is used to define the user interface
in "XML" you can save any hierarchical data.

In the above example the data of a telephone book is presented.
The book consists of people entries.
The data include each person's name, name and phone.

The data stored in the language of "XML" are plain text
and thus it is possible to transfer it between different systems.