If you right-click on a column heading in Layer Manager, one of the options is to Freeze the column. According to Help:
Freezes (or unfreezes) the column and any columns to the left. This option is available on the shortcut menu when you right-click a column heading.
AFAICT, all it does is put a gray line to the right of the column. Columns widths are still changeable, and all layer properties are still editable. So my question is, what does this do?