.SAVER File Extension
What is a SAVER file?
Screen saver for Mac OS X; runs when the computer has been idle for a specific amount of time; may be included with the Mac OS X operating system or created by a third-party developer.
Apple screen saver files are typically stored in the /System/Library/Screen Savers directory. Third-party screen savers that have been installed by the user are saved in the ~/Library/Screen Savers folder.
Screen saver settings can be customized by opening System Preferences and selecting the "Desktop & Screen Saver" Preference Pane.