The "Folders" and "Public Folders" are used to get a small overview of all local or public folders.
In later versions you used this to create / rename / delete folders.
These functions have been moved to the tree. (see Tree)
To open the folder in the maillist-view, click the underlined folder title.
Public folders are the same as normal folders, except they are
accessable (and writeable) by every user.
Deleting emails / folders inside the public folders moves them
to the public trash.
A public folder is automatically created for every user. (public
folders/$username)