This policy setting sets the "Alert before overwriting cells" option found under File tab | Options | Advanced | Editing ...

This policy setting sets the "Alert before overwriting cells" option found under File tab | Options | Advanced | Editing Options.If you enable or do not configure this policy setting, Excel will give a warning if cells are about to be overwritten.  This is the default behavior.If you disable this policy setting, Excel will suppress the warning that cells are about to be overwritten.