Why do we need GUID?

Hi All,

I noticed some posts on SDN forums talking about creating GUIDs and using them as primary keys in DB tables and Persistent Objects especially in CRM.

But I don't know why do we need GUID? aint the business key enough?

What are the uses of GUID?

I could not find any GUID fields in the standard tables in our ERP system (SAP NetWeaver 7.0)!!!

Could somebody please explain this to me or put some links on this matter.