Column: A folder provides a certain number of columns. A Shell column, since Windows Vista, is equivalent to a Property from the Windows Property System.

Explorer: Windows Explorer, implemented by \%windir%\System32\explorer.exe.

Junction Point: The root of a namespace extension is normally displayed by Explorer as a folder in both tree and folder views. Where the root folder is in the Shell namespace hierarchy is referred to as a junction point.

On-Demand: File On-Demand is a technology that was introduced with Windows 19 version 1709 (or “Fall Creators Update”). It allows users to see all their files stored on OneDrive from within the Windows Explorer, without having to first download these files. ShellBoost has exclusive support for this on-demand technology, with or without a Shell Namespace Extension support, through the OnDemandSynchronizer class.

PIDL or IDL: A PIDL (a Pointer to an Item Identifier List. For convenience, the term PIDL generally refers to the list itself rather than the pointer to it.) represents a Shell item in the Shell namespace. It’s like a file system path for a file or folder.

Property / Property Key: A property is an individual piece of metadata associated with a Shell item. A property, since Windows Vista, is equivalent to a folder’s column. A Property Key is a special binary value composed of a Guid and a 32-bit integer. A Property Key is the unique identifier of a Property. A Property also has a canonical name that represents it uniquely. For example, System.ItemNameDisplay is the canonical name, and its Property Key is {b725f130-47ef-101a-a5f1-02608c9eebac} 10. All ShellBoost folder columns use a property to define them.

Proxy or Native Proxy: The native C++ written assembly that provides cross process communication between Explorer and your Shell Namespace Extension server.

Windows Shell or Shell: The Windows Shell. To make things simple, let’s say it’s implemented by \Windows\System32\shell32.dll and Explorer is its host process on Windows desktop editions. There can be many explorer.exe processes running in a live Windows session.

Shell Item or Item: An item is an item in the Shell’s hierarchy. An item can be a folder. ShellBoost Core’s represents an Item by the ShellItem class. Quite logically, since a folder is an Item, ShellFolder derives from ShellItem. ShellItem has no technical relation to the native Windows’ IShellItem interface although they do represent the same object.

Shell Folder or Folder: A folder is an Item in the shell hierarchy that can contain other Items. ShellBoost Core’s represents a Folder by the ShellFolder class. ShellFolder has no technical relation to the native Windows’ IShellFolder interface although they do represent the same object.

Windows Property System: It’s an extensible read/write system of data definitions that provides a uniform way of expressing metadata about Shell items. The Windows Property system in Windows Vista and later enables you to store and retrieve metadata for Shell items.