A script file is a file that contains multiple scripts and functions. You can find a number of script files in the JAWS shared settings folder on your system. These script files all have the extension of .jss for JAWS script source. For example, the Default.jss script file contains all the scripts and functions JAWS uses to interface with Windows based applications. JAWS also uses application-specific script files. These files contain all the scripts and functions needed to access information in a given application. JAWS loads the application-specific script file on top of the default script file when you start the corresponding application.
JAWS loads the default script file each time it starts. The scripts and functions contained in the default file are active in all sessions. JAWS receives all the information it needs to provide proper voice output from the scripts contained in the default script file. The scripts within this file tell JAWS what to speak and when to speak it in most circumstances. The default script file is named Default.jss.
The second type of script file JAWS uses is specific to a Windows based application. You create an application script file when you encounter situations that require customized reading of the screen. JAWS loads the application-specific script file when the application is started or becomes active. For example, an application named SPREADSHEET.EXE has a script file called SPREADSHEET.JSS. The application script file must exist in either the JAWS shared or user settings folder in order to be loaded with the application at run-time.
When the spreadsheet application is no longer active, JAWS unloads the spreadsheet's script file. All of the default scripts then become active until JAWS loads another application's script file.