Difference between XElement and XDocument

Both are the classes defined by System.Xml.Linq namespace

XElement class
represents an XML fragment
XDocument class represents an entire XML document with all associated meta-data.

example:

XDocument d = new XDocument(
      new XComment("hello"),
      new XElement("book",
              new XElement("bookname", "ASP.NET"),
             new XElement("authorname", "techmedia"),
       )
);