ActionArgs.FilteredOrderRows

What does Litium.Foundation.Modules.ECommerce.Plugins.Campaigns.ActionArgs.FilteredOrderRows represent? What is it filtered on, how is it different from the order rows on the OrderCarrier? Why is this being manipulated in campaign actions in favor of manipulating the OrderCarrier's rows directly?

Litium version: 7.2.3

The value ActionArgs.FilteredOrderRows is pre-filled at creation time of the ActionArgs by using the value of ConditionArgs.FilteredOrderRows.
The order action does not filter anything. However, the campaign condition may filter the order rows and make certain order rows not available for campaign processing. Unless a campaign condition removes a order row, these two would be identical to the list of order rows.
A typical example is, if a campaign condition is operating on a particular product category only. In this case, the condition may filter out all order rows that has products that do not belong to the product category selected.