Batch job in sap crm

Hi Gurus,

     Can someone please describe me importance of batch jobs in SAP CRM? For what business process can we set up batch job in SAP CRM? What are the prerequisites to set up batch job in SAP CRM? What information do we need know, such as database tables, fields, to set up a batch job in SAP CRM? If you can suggest a document that teaches you how to set up batch job, it will be much appreciated.

Thank you,

Ajmal Siddiqui