There are three dynamic rule sets that can be enabled for a given metadata field:
1. Requirement - a field can dynamically be marked as required based on the value of another dropdown field.
2. Visibility - fields can always be visible or only visible based on the value of another dropdown field.
3. Choices - (only applicable to dropdown fields) filter the choices shown to the user based on the currently selected value of another dropdown field.
Cascading rules can ONLY be created based on the value(s) of a dropdown field. It is possible to apply all three rule sets to the same metadata field but as a best practice it is recommended to make each rule set dependent on the same metadata dropdown.