Items and meanings:
Enable Virtual Check this box to enable virtual server,
Server (1): and uncheck this box to disable virtual server.
Private IP (2):  | Input the IP address of the computer or network  | 
  | device which provides the network service.  | 
Private Port (3):  | Input the port number of the IP address  | 
  | which provides Internet service.  | 
Type (4):  | Select the type of connection, TCP or UDP. If you're  | 
  | not sure, select 'Both'. | 
Public Port (5):  | Select the number of the public port which will be  | 
  | redirected to the port number of the local IP address  | 
  | defined above.  | 
Comment (6):  | Enter any text to describe this mapping, up to 16  | 
  | alphanumerical characters; e.g., "FTP Server".  | 
Add (7):  | Adds the mapping to virtual server table.  | 
Reset (8):  | Remove all input values.  | 
Virtual Server  | All existing virtual server mappings will be  | 
Table (9):  | displayed here.  | 
Delete  | Select a virtual server mapping by clicking the  | 
Selected (10):  | 'Select' box of the mapping, then click 'Delete  | 
  | Selected' button to remove the mapping. If there's no  | 
  | existing mapping, this button will be grayed out.  | 
Delete All (11):  | Delete all existing virtual server rules.  | 
Reset (12):  | Unselect all mappings.  | 
Click 'Apply' (13) to save the settings.