To open the System file, double-click it. When open, the System file displays all of the fonts, keyboard layouts, and sounds installed in it --
as though it were a folder. While fonts and sounds are actually resources, they are treated as though they were simply files within a folder. (Because resources are special files, aliases cannot be substituted for them.)
You can double-click any font to see a sample of that font. You can double-click any sound to hear the sound.
Many of the functions that used to be contained in the System file have been moved to specific control panels. Modifying such things as icon layout no longer requires manipulation of the System file with ResEdit or other tools.