There are six alert types in Zenduty - Critical, Error, Warning, Acknowledged, Resolved, and Info.
Every alert coming from an integration source has an entity_id. If the alert source sends an entity-id, and the alert type is either critical, error, or warning, then that alert will trigger a single incident.
By default, the Create Incidents for setting is for Critical incidents only. Every alert after that with the same entity_id will be attached to the earlier created incident. An acknowledged alert type from the source will automatically acknowledge an incident and a resolved alert type will automatically resolve the incident.
So, incoming alerts from integration sources create an incident in Zenduty, and Zenduty sends notifications to your team based on your escalation policies.