To explain it (somewhat), they are a level of systems in pera-cosmology. The first Parafield is just an Itfield, all that can be contained. The second is all that can be contained, all that cannot be contained, the third is what is, isn't and in between being able to be contained, continue for all Parafields in an Ingen. Any n-ary field could be considered a shadow of the parafield at the same level (i.e, Binaryfield is the shadow of Parafield(2))
to describe its sheer size, you could say that this is a type of field that is contained within Ingena which contains all and everything. Almost everything in existence confuses this with The Box , but it is still not at that level, for The Box is absolute, forever, while this can still be paradoxically contained within something, for it has no rules other than it is all.
Parafields are only within reach of the best of omnipotent entities, untouchable by Aspect Lords of any kind, something below TTG but above Aspect Lords is at this level. If an entity, somehow, got here, it would be just fine, but no entity below TTG can reach this place with the power they possess. If some hyper-advanced species got here, they would define this as The Box, or whatever they would call it.