Configuring Kwizcom Cascading Lookup Plus Field for Sharepoint isn't always clear even if you've read the user guide. This YouTube video makes it a bit clearer.

It explains how the contents of a dropdown field can be filtered based on the selection you make in another dropdown field. These are sometimes referred to as "cascading fields"

In their example they select a 'Region' and this filters the 'Country' list which once selected filters the 'City' list.