Display Order
Display Orders are a legacy feature, gradually being replaced with an accessible drag and drop interface.
Display order is a way of controlling the order in which the options in a list appear. The bigger the display order number, the lower the item will display in the list. Think of it like a "weight" for each option, with heavier items moving to the bottom of the list, and lighter items floating to the top. If no display order is set (i.e. everything is 0), or several options have the same display order number, the list will revert to ordering alphabetically or numerically as appropriate.
The screenshot below shows the list of accommodation types. The display order is set to 0 for all options. However, the new drag and drop feature is visible on the left hand side and is the easiest method of adjusting the list.