References collection of sub-folders in current folder.

An ImapFolders object.  

object.SubFolders

The SubFolders Property syntax has these parts:

As IMAP protocol specifies, each folder can have unlimited number of subfolders (mailboxes) where user can keep his messages. User can create more folders and move messages among them (for whatever reason, typically for sorting them out).

Folders should be presented to you (and to the user) very similar as they exist on Windows OS - you can consider User.Folders property to contain his root folders (once again, INBOX belongs here), but each of such folders can contain subfolders and so on.

This hierarchy can depend on your IMAP implementation - you can allow users to create folders, but you can also create it for him - although user can ignore some of those folders completely.