By means of the C64U Menu many configuration options are available. Like for example to switch the video output from PAL to NTSC.

If you wish to run a game that expects specifically PAL or NTSC you can go to the C64 Menu and change the setting. Or you can create a configuration file in the same directory as that game to change that setting. Run that configuration file to switch the setting directly. And run you game.

It is a shortcut. Like a macro.

This MonroeWorld video gives a good overview how to use this.