SqueezeCenter (formerly known as SlimServer) is the servier software required to control the SlimDevices/Logitec range of networked music streamers. See
http://www.slimdevices.com/ for details.
Twonky is a UPnP server that makes your media available to uPnP capable devices. These are usually small, relatively cheap networked boxes wth oudio and video output. There are loads of these around.
Hope that clears if up.