Rygel is a collection of DLNA (UPnP AV) services (devices in UPnP speak),
implemented through a plug-in mechanism. UPnP in simplest words is a set of
protocols that defines how different devices on a home network can seamlessly
(without or with minimum configuration) communicate with each other. UPnP AV
defines how multimedia systems could be built on top of that. DLNA in simple
words is a long list of rules that implementers must comply to if they want
to achieve interoperability with other implementations in the market.