file is a command used to provide an overview of one or more files and identify the contents.
Here is an example from a console session:
tweedleburg:~ # file spider4.tar spider4.tar: POSIX tar archive (GNU) tweedleburg:~ # file amadeus.mpg amadeus.mpg: MPEG sequence, v2, program multiplex tweedleburg:~ # file tmp tmp: directory tweedleburg:~ # file /usr/lib/libQtCore.so.4 /usr/lib/libQtCore.so.4: symbolic link to `libQtCore.so.4.5.1'
Also, while it is customary to name shell scripts with a '.sh' extension, it's more economical not to and distro scripts are rarely named that way. 'file' provides a quick overview of what's a script and what's a binary when 'ls' merely displays a bunch of executables.