Question about “Computed Item” in IR Job action’s option

I have a question about the meaning of "Computed Item".

When run the IR Job, selected Action = "Import Document" in Cycle

There are 4 selections how to save the BQY in the Action.

The difference between “Results and Computed Item” and “Results and No Computed Items”

is

Save the “computed items” or not.

I created a simple BQY and did test. But I could not see the differences.

 

Could you tell me what is the “computed items”?