Administration: System Copy vs System Refresh

What is System Copy: To build a SAP system similar to Production data
1) Homogeneous system copy: source and target system using the same operating system and database system  (using database backup/restore)
2) Heterogeneous system copy/migration: source and target system using different operating system or database system (using SAP specific tools*). Additional info: http://scn.sap.com/docs/DOC-8324

What is System Refresh: Refresh existing system data with production data (target system is online)
1) Database Specific method (database backup/restore)
2) SAP specific method*

*SAP specific tools/method: R3load (for ABAP) and Jload (for JAVA)

       Create new DEV/QAS systems            Update existing QAS system with latest data