Four-dimensional space is different from three-dimensional space. Four-dimensional space refers to the standard Euclidean space, which can be extended to n dimensions. Four-dimensional space-time refers to a misunderstanding of Minkowski's concept of space. As a three-dimensional object, human beings can know four-dimensional space-time (three spatial dimensions (summarized by Newton) [length, quantity, temperature] and one time dimension) but can't know four-dimensional space, because human beings can't know the fourth-dimensional space dimension. Generally speaking, time is the fourth dimension, that is, the time dimension in four-dimensional space-time.
Five-dimensional space is the unity of time, space and level. In five-dimensional space cosmology, time, space and hierarchy are symmetrical. Symmetrical space view is the essence of five-dimensional space view, and five-dimensional space view is the expansion of symmetrical space view. So the view of symmetric space is the view of five-dimensional space.
"Six-dimensional space" refers to a hypothesis put forward by physics at the University of Wisconsin-Madison, that is, on the basis of physical string theory, there should be six other spatial dimensions besides three-dimensional space and time. These "hidden" spatial dimensions are curled up at every point in our universe with extremely tiny geometric shapes. Six-dimensional space can accept any possible shape, and it is consistent with its own world and has its own physical laws.