What is the difference between a directory and folder?
A directory and folder are the same thing. The Windows folder on the C: drive of Windows is the same thing as C:\Windows in MS-DOS. Therefore, there really is no difference between the two, other than the names.
However, when referring to a command line interface such as MS-DOS or Linux it's more correct to say directory instead of folder. In a graphical user interface (GUI), such as Windows, it's more correct to say folder instead of directory. An easy way to remember this rule is that when viewing the folders and files in Windows the folders will have pictures of folders, as shown in the picture. In a command line, there are no pictures of folders.