Typically, both people walk, using good Bluetooth headphones.
I was finding the combination of staring at the screen while coding, and then also during meetings, to be very straining.
Something about having to focus intently on the screen during a 1:1 was particularly tiring. Maybe because it's socially rude to look away while the other person is talking, so you end up really staring at the screen?
Now, instead, during a walking meeting, I exercise and get to look into the distance.
The most surprising thing for me was the ability to have technical conversations like this. I expected we'd really suffer without a whiteboard. Sometimes this is true, but I find we can have a lot of very technical conversations with voice only, and actually it's often easier than with video chat - because with voice only, I can focus more on the technical issues being discussed.
Finally, there are some days where I have a couple of hours walking meetings scattered throughout the day, and this is a lot of extra movement, which has to be good.
I wish there were more employers experimenting with different communication modalities like this; I feel the pandemic for all it's costs, has shown there are some great opportunities for other ways of working which have been underexplored.