Nadi Shodhana is breathing through one nostril at a time in an alternating fashion. It is, among other things, an exercise in concentration. It can be layered over other breath practices to amplify the effects.

Super important: In the video, I start counting down from 27. You don't have to get all the way to 0 on your first attempt. Or even your fifth. Or ever. Pause, rest, or stop if it's hard work to do the breathing exercise itself or to concentrate on the counting or alternating.

I don't recommend using this video over and over and over. Once you get the hang of the rhythm, it's better to build your own practice rather than just following along with the counting and alternating.