XML is a type of coding language referred to as a markup language. HTML is another markup language.

It defines a set of rules for formatting documents that can be easily read by humans and computers.

It uses tags to categorise the content and aims for those tags to be self descriptive – the terms used within the markup describe what it is that it will do.

For example:

<shoppingList date="13/11/2011">
  <item>
    <name>Bread</name>
    <numberNeeded>1</numberNeeded>
  </item>
  <item>
  <name>Tomatoes</name>
   <numberNeeded>4</numberNeeded>
  </item>
  <item>
    <name>Potatoes</name>
    <numberNeeded>10</numberNeeded>
  </item>
</shoppingList>