There are numerous definitions for the term “back channels” if you were to look this up on the internet. A back channel can be as simple as students or conference attendees using IRC or instant chat to discuss a lecture among themselves. The lecture or talk is the “front channel” (formal presentation) while the chatter being the back channel.
A back channel can also be attendees of a webinar or conference posting comments to each other as the speaker is presenting.
Taking a publicly posted commentary on Facebook, and continuing the dialogue on instant messaging (Facebook messaging) can be another back channel. I’d venture to guess there’s more dialogue going on via private messaging than there is in the visible status update sections as behind-the-scenes people are willing to divulge their opinions more openly and discuss topics of a sensitive nature.
As a result the conversations are often livelier and more informative in the back channels than they are in the formal mode. The military and federal government state departments use back channels for obtaining tips from informants.