What is a navigation tree?
A navigation tree is a graphical user interface, that displays a hierarchical data structure in an expandable tree like diagram. One of the first programs to make use of a navigation tree was the wonderful XTree, which displayed DOS directories as a tree.
What are alternatives to TreeView?
The best alternative is Archaeopteryx, which is both free and Open Source. Other great apps like TreeView are FigTree, TreeView X, UGENE and Dendroscope.