C programming: What does this construct in printf(_(" means?

[shaulka@bezeqint.net]

What does the construct

   _("What ever format string I use")

means in the context of printf?

For example:

[00:50:20 tmp]$ grep -C1 printf\(_\( util-linux-2.11b/misc-utils/script.c
                if (!strcmp(argv[1], "-V") || !strcmp(argv[1], "--version")) {
                        printf(_("%s from %s\n"),
                               progname, util_linux_version);
--
        if (!qflg)
                printf(_("Script started, file is %s\n"), fname);
        fixtty();
--
                if (!qflg)
                        printf(_("Script done, file is %s\n"), fname);
        }
[00:50:33 tmp]$

-- 
    
    Shaul Karl <shaulka@bezeqint.net>

Hillel used to say: If I am not for myself who will be for me?
Yet, if I am for myself only, what am I? And if not now, when?
                                          (Ethics Of The Fathers 1:14)