If "Subscribed Lists" is selected (the default), only lists that you are subscribed to are displayed. If "All Lists" is selected, all lists on the server that you are subscribed to, and any public lists on the server that you are not subscribed to, are displayed. The selection of lists is also subject to the setting of the "Narrow Selection" box. Lists that you are subscribed to will be highlighted with a clickable link. Changes submitted while the "All Lists" box is checked will affect only the lists that you are currently subscribed (and of those, only those where you have checked the box to the left of the list name), with the exception that you may subscribe to any list displayed to which you are not currently subscribed.
See the LISTSERV Manuals for complete documentation.