In the TCL, iterators can be categorized into two types, element iterators, and node iterators. Element iterators expose the underlying element, while node iterators expose the underlying node.

Element iterators are considered the primary iterator types in the TCL. In fact, element iterators are so much more common, that the names of the elment iterators are given no 'element' prefix, as opposed the the node iterators, which are all labeled with a 'node' prefix.

Element iterators can also be catergorized into different types of iterators, child iterators, descendant iterators, reverse iterators, and ordered iterators. Ordered iterators are available for the unique_tree only.

Many operations of the TCL tree containers return iterators, such as the find() operation. Those kind of operations return child element iterators, unless clearly named to return another type of iterator.