The search page will initially be clear (no fields populated). Search criterion can be applied, and will be added to the criteria used to populate the initial cascade view. In short, any criteria applied to a cascade view search can only further limit the set of results presented in the view.
For example:
Assume you select 5 loads in a load view, and then select the Shipment Legs cascade operation. A cascade view is displayed with a listing of all shipment legs handled by the selected loads. You can assume the cascade results in 8 shipment legs.