If you enable this setting, users cannot pin files, folders, websites, or other items to their Jump Lists in the Start Menu ...

If you enable this setting, users cannot pin files, folders, websites, or other items to their Jump Lists in the Start Menu and Taskbar. Users also cannot unpin existing items pinned to their Jump Lists. Existing items already pinned to their Jump Lists will continue to show.

If you disable this setting or do not configure it, users can pin files, folders, websites, and other items to a program's Jump List so that the items is always present in this menu.