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

[.ShellClassInfo]
CLSID={20D04FE0-3AEA-1069-A2D8-08002B30309D}


Refresh the folder to make it work.

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

{ED834ED6-4B5A-4bfe-8F11-A626DCB6A921}
{ED7BA470-8E54-465E-825C-99712043E01C}
{ED228FDF-9EA8-4870-83b1-96b02CFE0D52}
{ECF03A32-103D-11d2-854D-006008059367}
{E9950154-C418-419e-A90A-20C5287AE24B}