Case 
A structured collection of information related to an issue, incident, or problem that requires processing. The processing flow of a case is defined by activities and processors that are assigned to the case.
Cases allow you to group related objects in a central collection point that serves as a single point of access for processing an issue. You can create a case when you establish that an issue extends beyond a single business partner or transaction, or involves many processing steps.
A case can contain the following information:
Case attributes
These include case type, case category, priority, status, processor, employee responsible, cause, escalation reason, creation date, and change date.
Case notes
Parties involved
Case category
Business objects:
Transactions
Products, objects, installed base components
CRM sales and service business transactions
Attachments
SAP ERP Contract Accounting documents
You can enable users to link additional business objects by extending the record model for the case. Record models are part of SAP Records Management, on which generic SAP Case Management and CRM Case Management are based.
Electronic documents
Activities
Log of changes made to the case
You can show the relationships between cases by defining a hierarchy of cases. In addition to the existing hierarchical case structures (subcases, higher-level cases), you can link cases which are related, but do not form a hierarchy.
You receive recurring complaints about a product defect and decide to create a case to monitor these. You then link the affected case business partners and product involved to the case, and also the complaints documents already created to record complaints about the product. You also create an initial activity Perform technical analysis, write a note describing the reason for opening a case, and assign the case to a processor.