To me, Interaction design is all about influencing behavior.
Each user’s behavior leads to (or from) fulfillment of their own goals as well as fulfillment of those of the service’s owner.
The service’s behavior (feedback, flows, categorizations etc) influence how efficient and usable the user feel that the service is. People often experience that systems have a”personality” and it is, to large parts, built by the system’s behavior in combination with it’s graphical design.
Behavior by the owner of the service, often represented by employees, affect how users experience the service. Personnel in editorial, support, sales, and other customer facing roles therefore need to be encouraged to reflect over how their behavior influence users. The behavior of executives also influence the service.
To enable users and service owners to reach their goals I, the Interaction Designer, need to influence behavior on all three levels: The user’s behavior, the system’s behavior and the owner’s behavior.