The Spring XML configuration uses XML namespaces, which is good practice when you use XML. It allows tools like your IDE to understand what the XML means and check it against an XML Schema (XSD).
If you want to compare it to Java, namespaces are a little bit similar to packages in Java. And just like when you write a program in Java it's always a good idea to put your classes in a package, it's always a good idea to use namespaces when you work with XML.
Thanks for your anwsers, sorry for the title but I don't know how to edit my post.
The special thing about Spring reference is I don't understand what they are talking about until I have some questions in mind and then reread it