InstallMate sets this variable to the name of the current action, for example Installing files.... This variable is used to provide progress information in the installer's user interface. For standard actions, the installer uses one of the Messages; for custom actions, this variable is set to the action's Description attribute.
You can refer to this variable as <TsuActionName>. It is set and updated automatically by InstallMate, but you can also use a Set Variable value to set its value during installation.