It only fill a URL var of your choice, basing on the current CID of the item.
For example you have a table 'ITEMS' with a FK to 'FAMILY'
When you finish editing a new FAMILY, you can redirect to a list of ITEMS filtered on this family.
In this example, only write 'filter_family'.
So, just after, if you click to New (ITEM), this form is prefilled whith the current FAMILY (because it is filtered)
It is much more ergonomic.
You can reuse the 'cid' of the item for whatever url var you want, after task execution.