Delta events are good at capturing the intent behind the creation of the event, and provides context for the event’s consumers. A cart fact models the portion of the cart state that we want to publicly expose

to other consumer services in our organization. With delta modeling, we instead select specific state transitions, and build a model that describes the change, not the state. Delta events are very well-suited for exposing specific transitions in a system to downstream subscribers. Delta events provide a partial set of information that is usable for the consumers to act upon with their own business logic.

Confluent

Fact vs. Delta Event Types | Events and Event Streaming

Source

Also known as “Action Events”, used in Event sourcing