In Xport and XportPro, child iterators are used to iterate over the immediate children of a particular xhtml element. These iterators work like and use the same conventions as those iterators in the STL. There is a const and non-const variety of the child iterators in Xport/XportPro. The non-const variety is named iterator, and the const variety named const_iterator just as in the STL.
You'll normally use iterators to perform any traveral over any element's children. For instance, an iterator of the <body> element will traverse over those immediate children (elements, comments, markup, etc) within the <body> element.
While child iterators traverse the immediate children of a particular xhtml element, descendant iterators traverse descendants of a particular xhtml element in a pre-order fashion.