There’s no separate executable for command-line tasks; the regular inkscape (on Linux or Mac OSX) or inkscape.exe (on Windows) will work as a command-line utility if you give it the corresponding parameters. The simplest use of the command line is providing the filename(s) of the document(s) you want to load into the GUI. For example:
$ inkscape file.svg some/other/document.svg another/file.pdf
will start Inkscape’s GUI and load the two SVG documents and one PDF document (automatically imported) into three Inkscape windows. In this case, no task is given to Inkscape, so it simply lets you edit the files. As we will see later, other command-line parameters, usually starting with --, will force it to skip the GUI and do something to the files on its own.