Unless you are a member of ITU-T Q4/15 (don’t lose interest, all will be explained) you probably don’t know much about the standard. Not surprising. Unlike the final standards (the ITU calls them “Recommendations”), which are available to anybody, the working texts are only available to members.
The ITU operates under the United Nations. Wikipedia has extensive entries about both the International Telecommunication Union (ITU) and which is the part of ITU that develops the standards. ITU-T is big and involved in a wide range of standards.
ITU-T is broken into “Study Groups” (SG) which are further broken into “Questions” (Q) which are also groups (still with me?). G.hn is part of SG 15 Question 4 or Q4/15 (simple, right?). Q4/15 is an important group also develops the international DSL standards. It includes major service providers such as AT&T, Verizon, BT, France Telecom, Qwest and others as well as many of the leading communications equipment vendors. Standards for transmission systems and media, digital systems and networks are numbered starting with a “G” – so G.hn for home networking.