Areas of responsibility.
Direct consequences of user action.
Can invoke an aggregate or invoke an external system.
Receives commands and decides whether to execute them or not, thus producing a domain event.
A Domain Event is something meaningful that happened in the domain.
Basically is the Database table responsable to save the events triggered.
From the Domain Events we create the Read Model. The UI consumes the read model.
Different sub areas of responsibility.
Boundaries between the multiple consistent models that will coexist in your domain.
The persons triggering the actions.