A talkgroup is an assigned group on a trunked radio system. Unlike a conventional radio which assigns users a certain frequency, a trunk system takes a number of frequencies allocated to the system. Then the control channel coordinates the system so talkgroups can share these frequencies seamlessly. The purpose is to dramatically increase bandwidth. Many radios today treat talkgroups as if they were frequencies, since they behave like such. For example, on a radio scanner it is very common to be able to assign talkgroups into banks or lock them out, exactly like that of conventional frequencies.
It was this explanation (along with BART iconography) that made me land on this domain name. We bring in individual, distinct frequencies, and coordinate them into new conceptual channels, talkgroups. For anything, x, y, or z.