According to MSDN:

A CLSID is a globally unique identifier that identifies a COM class object.

CLSIDs can be used to create system folders such as My Computer, Control Panel, etc. There are two ways of using a CLSID:

  1. Make a folder, and name it FolderName.{20D04FE0-3AEA-1069-A2D8-08002B30309D}. You’ll see a My Computer icon. Open it and it functions just like My Computer.

  2. Make a folder. Put a desktop.ini file in it with the content


    Refresh the folder to make it work.

Various CLSIDs can be found in HKEY_CLASSES_ROOT/CLSID. Here are some of them: