A backchannel is a, typically, online conversation, that occurs hand in hand or along side another activity. It may occur as a conversation while students are watching a video in social studies. It may be where students post their questions during a conversation or learning session in science. It may be where students post their question or comments about a story they are reading. It may be where the teacher poses a question and then watches the responses to see if the proper depth of learning has occurred.
In any case, it is a place where the extension of the discussion and questioning can occur. What is great about this is that a backchannel is not inhibited by time or speed. If a student needs more time to think, they can take the time they need to process and think through their questions and then post them. In a real time discussion, the speed is determined by the students and some students get left in the dust. The other great benefit is that most backchannel tools create some sort of transcript file of the conversation. To read more about the power of a backchannel in your classroom, read this article on eduTopia.