After launching a remote session, the Client starts the Remote Display Server on the remote host where it creates a virtual window. The Server then sends the virtual window to the Viewer window running on your system. The Viewer is just another window running on the Client’s system. You can interact with the Viewer window in the same way you interact with any window that runs directly on your system.
Behind the scenes, your interactions are sent to the Server, and the Server interacts with the virtual window running on the remote host. Changes made by this interaction are sent to the Viewer on your system. Performance depends on the load on the remote host and network latency.