A pane or panel is typically something that runs down the side of a window, typically the left side.
The "Navigation Pane" found in Windows Explorer displays a hierarchical tree view of the subfolders in the selected folder, if any, and the + and - buttons alongside the items in the tree can be clicked to show the contents of other folders.
Such a pane may be found in other applications, although I do not know of any that do so.
Navigation Pane
Left pane or Navigation pane
Browser pane is an area at the top of the browser which consists of search window and navigation window.
Navigation pane
The Access Window
recent searches
answer
tables and related views
navigation pane
File list
navigation pane
The Shutter Bar Open/Close button is used to open and close the Navigation Pane in MS Access.