A. An RDS Session Host (RDSH), which was previously known as a terminal server, is the box that multiple users connect to for their sessions. RemoteFX has several components, including the use of a virtual GPU, enhanced USB redirection, and an enhanced encoding/decoding capability for the RDP protocol.
Sessions to an RDSH box with SP1 can take advantage of the RemoteFX enhanced encoding/decoding for the RDP protocol, but won't be able to use the virtual GPU or the enhanced USB redirection.
The virtual GPU (server side rendering) and enhanced USB redirection (which requires the virtual GPU be present) capability of RemoteFX is only available to Windows 7 Enterprise and Ultimate guest OSs running on capable Hyper-V boxes.