A 0-Dimensional Space is a space in which every position can be described in a point. In other words, there is only one possible position in zero dimensional space, so no information is needed to describe the location.
Strictly, a zero dimensional space will have no time or space so it will be in a fixed and single state, though sometimes spaces with some time dimensions (such as 0+1 dimensional space) are considered to be zero-dimensional.
A verse that is zero dimensional is called a protoverse.