|Noun||1.||traversal - taking a zigzag path on skis|
|2.||traversal - travel across|
|(data)||traversal - Processing nodes in a graph one at a time, usually
in some specified order. Traversal of a tree is recursively
defined to mean visiting the root node and traversing its
children. Visiting a node usually involves transforming it in
some way or collecting data from it.|
In "pre-order traversal", a node is visited _before_ its children. In "post-order" traversal, a node is visited _after_ its children. The more rarely used "in-order" traversal is generally applicable only to binary trees, and is where you visit first a node's left child, then the node itself, and then its right child.
For the binary tree:
T / I S / D E
A pre-order traversal visits the nodes in the order T I D E S. A post-order traversal visits them in the order D E I S T. An in-order traversal visits them in the order D I E T S.