If you see DVR in the upper left-hand corner of the video, it means that you are watching the live stream video with some time delay.  As such, you may miss cues to ask questions or other live participation cues.

This happened because of one of two reasons: 

1) slow internet connectivity, or 

2) you paused the video and then clicked play a few moments later—so now you are watching where you paused, not the live stream. 

To skip ahead to the live stream in real time, click the button to the right of the play button (  >| ).  This will return you to the real-team live stream and you will see LIVE in the upper left-hand corner of the video.