"/" Is a node that represents the current document, similar to the DOS directory split. For example: / people represents the people elements under the root node; People / Person represents all the Peson sub-elements under the people.
"//" means all nodes of the current document. Similar to view the entire directory. For example: // people indicate what the people have all in the document, whether it is what level; people // person represents all the Person elements under the people of the People, no matter how deep it.
