It’s just a normal folder that is added by default in new Syncthing installations, so that the user has got something to start with. You can use it if you want, or remove it if you don’t need it.
I would even say that it may not be useful at all. After all this is an empty folder that is not shared with anyone (as opposed to, say, Dropbox or Nextcloud where the folder is automatically shared/synchronized somewhere).
Either someone already has data to synchronize (and therefore shares the folder), or would create it themselves. I would be curious how many people actually use that default folder (maybe there is some telemetry on that?)
It’s easier to share then normal folders though, as its ID is fixed as default, so you don’t need to go through the whole procedure of adding a new folder if you share it between already connected devices.
ahh, I did not realize that. So it means that by the mere fact of having a device paired, this folder will be automatically common - that’s indeed a nice feature (maybe this needs to be more explicit in the docs/quick start)