This is a portion of the Gather Town environment. You control your avatar (mine is only one visible because this is several days after the convention) and can customize it to some extent. You move around the environment (there's more than what's visible here) and when your avatar gets closer to others, you can start to hear and see (assuming they have their microphone/camera turned on) them and they you.
What I liked about this was it was more like a party environment, in that there were multiple conversations going on in different parts of the environment, and you could move to other areas relatively easily. As it happens, I ended up spending most of Friday hanging around in the ad hoc Australia Worldcon bid party, that being where members of their bid committee were congregating.
An advantage of this environment is that, unlike the Zoom parties, you can have multiple conversations in the same room, and I think that makes for a better simulation.
Not everyone was as fond of Gather Town as I was. I'm sure there are ways it can be improved. As it happens, I'd prefer ActiveWorlds as an even better simulation, except that they apparently never did get the voice discussion working. I'll be interested to see if Gather Town does develop into a more robust socializing tool.