What is the difference between a directory and a folder?

Question

Most people use the terms \"folder\" and \"directory\" interchangeably. From a programmer point of view, is there a difference, and if so, what is it? Does it depend on the OS,

Answer 1

I didn't know the difference between these two words in English before, even in the Windows registry editor I could found two sub-keys, Folder and Directory, under HKEY_CLASSES_ROOT.

I didn't know the difference until I created some values manually in registry and observed the differences of context menu items. If I create a node under HKEY_CLASSES_ROOT\Folder\shell only, I found that it appears in the context menu of both the virtual folders (aka system directory), like Recycle Bin, and the file system directory, like C:\Windows.

If I create a node under HKEY_CLASSES_ROOT\Directory\shell only, it only appears in the context menu of the file system directory, like C:\Windows, but not a virtual folder. So, like @AntonyW said, in Windows, folders = virtual folders + file system directories.