Directory specifies that directories within the current directory are shown before other files.
Size specifies that the size of the file determines the order in which files are displayed.
Date specifies that the date of the last change to the file determines the order in which files are displayed. If the dates are the same, the time the file was last changed is used as a secondary sort key. Time specifies that the time of the file determines the order in which files are displayed. Name specifies that the name of the file determines the order in which files are displayed. This is the default.