These are a groups of cohesive actions. These are typically called 'cases' in the web application. The web application's terminology section allows these to be renamed, but they are always called 'referrals' in the API.
Only referrals made using a template are available in the API. Since version 888 of the web application, launched in October 2020, templates are automatically created when new projects are created, so that all referrals are available in the API. If you are still running version 866, launched June 2020, please update to version 888 before using referrals in the API.