It is never a good idea to execute an application when not knwowing what it does (especially by passing command line options). Do such at least as normal user and not as root.
With many applications there is a man page installed too. So you should first try if such is available:
man scan
and
info scan
That should explain the purpose of the program and what the options are doing when present.
Most Linux applications provide an option to show help about the available command line options. This option is usually
-h. So try executing (at your own risk)
scan -h
If that lists the avaible options, check for an option showing the program version (usually
-V or
-v). The output will often contain a more informative name of the application / product. The list of options will also contain a short description for the
-a and
-C options.
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