That's not a site I'm familiar with; I'll give it a look when time permits.

The one thing I can think of that more or less corresponds to it is that human beings have bodies on the three lower planes -- the material, etheric, and astral planes -- and we're in the process of evolving bodies on the fourth, the mental plane. The three planes beyond that, the spiritual, causal, and divine planes, aren't within our reach; they can affect us but we can't perceive them.