One of: element, attribute, text, cdata, comment, chunk and (EXPERIMENTALLY!) entity_reference. A chunk is a character string which forms a well-balanced piece of XML.
add element hobbit into //middle-earth/creatures; add attribute 'name="Bilbo"' into //middle-earth/creatures/hobbit[last()]; add chunk '<hobbit name="Frodo">A small guy from <place>Shire</place>.</hobbit>' into //middle-earth/creatures;