From FCKeditor Docs

The File Browser Requests

All requests are simply made by CKFinder using the normal HTTP channel. The request info is always passed by QueryString in the URL that uses the following format:

connector.php?command=CommandName&type=ResourceType&currentFolder=FolderPath

CommandName

The command the Connector is required to execute.

ResourceType

Indicates the resource type to which the request refers to. A resource type is a way to group specific kinds of files in groups which can be configured separately.

FolderPath

The path of the folder to which the command is to be applied. This path is not the final URL path for that folder, but it is relative to the Resource Type folder. The final folder is composed by: "Resource Type Folder" + "Folder Path". For example, the Folder Path "/Docs/Test/" of resources type "Image" could correspond to the following URL path: "/userfiles/image/Docs/Test/".
The Folder Path must always begin and finish with a slash ("/").