You can verify the file system of the volume which is currently defined as startup disk. Note that an enforced check with an automatic repair of the startup volume is usually performed when starting the Standalone Utility. The repair is automatically repeated when necessary, so it should never be necessary to run an additional manual repair from within the program. Only an additional verification can be run in this menu.
This feature is designed for cases where the operating system’s main folder for temporary objects has been deleted. If this folder is missing, many parts of the system will no longer work. Some applications may show the error message that the folder named /tmp cannot be found. In that case you should recreate or repair the folder. It is harmless to use this function at any other time, however. The program is checking automatically whether repair is necessary or not.