This article provides a definition for Real Servers (or Rservers)

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Real servers or rservers are dedicated physical servers that are added to your environment when you add a Server to a Server Farm. These servers provide services to clients, such as HTTP or XML content, streaming media (video or audio), TFTP or FTP uploads and downloads, and so on. You identify real servers with names and characterize them with IP addresses. 

Before you can start sending connections to a real server, you must place the server in service.

You can shut down a Real Server gracefully by taking the Real Server out of service.  This causes a reset to all non-TCP connections to the server. For TCP connections, existing flows are allowed to complete before taking the real server out of service. No new connections are allowed.