Hi Karim,
There are so many links you can refer to start with.
Please see below.
http://help.sap.com/saphelp_erp60_sp/helpdata/en/61/7dce53118d4308e10000000a174cb4/content.htm?frameset=/en/89/7cce53118d4308e10000000a174cb4/frameset.htm¤t_toc=/en/af/7dce53118d4308e10000000a174cb4/plain.htm&node_id=51&show_children=false
Regards,
Bodhisattwa