Its just a filesystem and is essentially the same as tmpfs. It is the kernel part of the volume
I suspect this is Fedora
It isnt taking up any space as it will simply grow alongside tmpfs and can not be deleted. I assume its like a balloon inside a balloon, the inside one is tmpfs and can be written to by admin, the outside one just gets larger as tmpfs grows and is part of the kernal
That is all i know, and this might not be correct
Albert