createDocumentFragment creates an empty document fragment
SyntaxdocumentFragment = element.createDocumentFragment
documentFragment is an object.
A documentFragment is a "lightweight" or "minimal" document object. It is very common to want to be able to extract a portion of a document's tree or to create a new fragment of a document. Imagine implementing a user command like cut or rearranging a document by moving fragments around. It is desirable to have an object which can hold such fragments and it is quite natural to use a Node for this purpose.
While it is true that a document object could fulfill this role, a document object can potentially be a heavyweight object, depending on the underlying implementation. What is really needed for this is a very lightweight object. documentFragment is such an object.