A background job in an AS ABAP-based SAP system is a program that runs in the background without user interaction. A background job can be started by two types of start conditions: time-based or event-based. A time-based start condition specifies a specific date and time when the job should start. An event-based start condition specifies an event that triggers the job start. An event is a message that is sent by an application or the system to signal that a certain condition has occurred. For example, an event can be the completion of another job, the creation of a file, or the arrival of an IDoc. Reference: [SAPTEC], Unit 5: Background Processing, Lesson: Scheduling Background Jobs, Slide 8-9; [ADM100], Unit 5: Background Processing, Lesson: Scheduling Background Jobs, Slide 8-9.