An
outliner (or
outline processor) is a specialized type of
text editor (
word processor) used to create and edit
outlines, which are
text files which have a
tree structure, for organization. Textual information is contained in discrete sections called "nodes", which are arranged according to their topic–subtopic (parent–child) relationships, sort of like the members of a
family tree. When loaded into an outliner, an outline may be
collapsed or expanded to display as few or as many levels as desired.