XPath expressions have a directory-path-like syntax.

A single "/" (forward slash) represents the Document info item--also know as the root.

Subsequent named "steps" in the path represent children:

/doc/title

selects the 'title' child element of the document element 'doc'.

But they don't have to be "rooted":

contents/para

selects the 'para' child element of the 'content' element.