Hyperspace

Since the early 1980s, many physicists had suspected that space contains more than the familiar three dimensions, corresponding to directions in which movement is possible (up-down, forward-backward, and sideways). Three directions is enough for everyday life, but not enough to explain how gravity fits together with the other forces of nature.

One explanation for gravity involves explaining basic particles (energy and matter) in terms of tiny vibrating loops known as superstrings. But for the math of superstring theory to make sense it is necessary to postulate a hyperspace or higher spatial dimensions beyond the usual three.  These extra dimensions exist at an extremely tiny quantum physical scale

Quantum physics