The idea of cascading filters is that as a user makes certain selections then xDM can limit other selections. A common example is the linked ideas of Country → State → City as shown in this diagram:
As you enter a person, when you select a country then your options for State and City should be limited by the parent value.
Setting up Steppers
The key concepts are that while entering data in a Stepper you are selecting values that are References to another entity. You can define a Filter for the Picker which allows you to pick values from the referenced entity. Here's an example from the data model shown above:
In this example, the Stepper is allowing the end-user to create a "Person". Therefore Record refers to the Person and Referenced refers to the referenced Country, State, or City. The filter on the State field depends on what the user has already chosen for the Country. So we use this filter to show only States (Provinces) within the specified Country:
Record.FID_CascadeCountry = Referenced.FID_CascadeCountry
The result is that values are limited for the end-user as intended:
Notice how xDM applies both the auto-complete filter and shows only records matching the string the user has typed as well as the filter imposed by the Picker Filter. California and Minnesota have different cities from each other. China has different States (Provinces) than the US has.