Such COM servers are called namespace extensions . Both the original Windows Explorer shipped with Windows 95 and the Web-updated version that many Internet Explorer users have support namespace extensions, so the technical considerations exposed in this article apply to both. The left pane of the main Explorer window is a tree view of the shell folders.
Shell folders can have children.
The right section of Explorer is a view of the selected folder. It is usually a list view or a web view. Through specialized interfaces the namespace extension can also support optional features such as custom icons, custom context menus, and drag and drop. Finally, it can also customize the menu and toolbar of the Explorer window itself. This interface is already implemented by Explorer and does not need to be supplied by the namespace extension.