Background Processing:
Programs can execute in the background of the SAP system while online operation is occurring. SAP’s background processing system is easy to use and completely integrated within the system.
Suppose a manager wants an weekly accounting report every Monday morning. This report can be scheduled to run automatically every Sunday night so that the report is available to him/her next morning.This scheduling of a report program is accomplished with SAP’s background processing system. This saves manual online execution efforts for repetitive jobs in SAP.

Work Processes:
The SAP R/3 Dispatcher and it’s work processes constitute the R/3 Runtime System. From the perspective of the host operating system, the R/3 Runtime System appears as a collection of  parallel processes.
On each application server, these parallel processes include a dispatcher and work processes, the exact number of work processes is variable and depends on the specific configuration (configured by BASIS team to meet the needs of the users of the system)

Transaction SM50 (Process Overview) gives details on a given application server’s work processes.
There are five types of work processes:

• Dialog [DIA]:  (or online) Work process for executing dialog steps in user transactions

• Update [UPD]:  Work process updates the database

• Enqueue [ENQ]:  Work process for setting and releasing locks on SAP objects

• Spool [SPO]: Work process for spool formatting

• Background [BGD]:  (or batch) Work process for executing background jobs

Up till now most of the interactions with the system have been handled by the dialogue work process (i.e. Saving/generating ABAP programs,  running transactions, etc.) To run jobs, however, we need to understand a new work process called the Background (or Batch) Work Process.

Background processing enables you to plan the start of ABAP programs. Then, at the specified time, they are executed by special work processes called background (batch) work processes.
Background processing runs are composed of jobs. A job is a sequential series of steps that can be scheduled.A step is a program for background processing.

The three phases of background processing are:  Job Scheduling, Job Processing, and Job Overview.
Before we cover these phases, it is important to mention that authorization objects exist for background (batch) processing:  S_BTCH_ADM, S_BTCH_JOB, S_BTCH_NAM, and S_PROGRAM.  Not all users will have the authority to release or manage background jobs.
In the next chapter we will learn about Job Scheduling phase.