1. Dialog
2 .Update
3. Background
4. Enqueue
5. Spool
Dialog work process : It deals with requests from an active user to execute dialog steps.
Update work process : It executes database update requests.
Background work process : It is used to process background jobs i.e. the programs that can be executed without user interaction.
Enqueue work process : It handles the lock mechanism.It administers the lock table(in shared memory area),which stores the logical database locks for SAP system.
Spool work process: It passes sequential datasets to output devices like printer,fax devices etc.
The Dispatcher gathers the requests from the front-end and assigns the tasks to the work processes that corresponds to their type.
Transaction code for Work Process Overview is SM50