What are various types of servers in SAP R/3

291- Sand Box server (Initial Testing scenarios Server)
292- Development Sever (With client data of minimum 15 days transactions)
294- Testing Server (the scenarios developed in development server is tested here)
295- Golden Master Server (Quality cum Testing Server) - checked finally before transferring to production server
296- Production Server (where the clients live data is stored and daily business transactions are done)