Show cause is generaly issued befor the Charge sheet.
It is A chanse given to employee on natural justice law that why did he commited the concerned indiscipline? was is done intentionaly or it was just mistake. He is being asked to respond in stipulated time to show cause.
on the other hand Charge Sheet is a first step decision of the management on the basis of facts available and individuals responese against Show Cause.
Regards,
Rahul