XPath selectors and XQuery scripts are used throughout the configuration API of Fonto. They are expressions, used as a filter.
If an XPath query matches a node (like self::element/child, an element with the name element and a child node named child, we say this node 'matches' the 'selector'. The element will be targeted by the configuration using this selector.
(: Note that, while unusual, it is also possible to use XQuery in XPath tests: :) declare namespace x="http://www.w3.org/1999/xhtml"; self::x:p and parent::x:div