The shell is an application that enables users to group, start, and otherwise control other applications.
Win32-based applications can extend the shell in a number of ways. A shell extension enhances the shell by providing additional means of manipulating file objects, by simplifying the task of browsing through the file system and networks, or by giving the user easier access to tools that manipulate objects in the file system. For example, a shell extension can assign an icon to each file or add commands to the context menu and File menu for a file.