These are the “worlds” which the Tzaddikim inherit. For example, with the emanation of Chochmah from Keter, three hundred and ten complete trees came into being (for Chochmah is yesh me’ayin, “existence out of nothingness”, and the letters of יש, YeSh, have the numerical value of 310). This is the secret of the three hundred and ten worlds of the Tzaddikim (Uktzin, 3:12; Zohar loc. cit.). In addition, there are the worlds of the souls, for each soul is a major root in the governmental order, and each soul has a tree of its own.
This is the meaning of the statement in the Zohar (loc. cit.) that each Tzaddik has a world of his own – i.e. the Tzaddik himself is the world. One who attains only his own root takes his world. But one who attains everything receives the entire emanation of Chochmah, which consists of three hundred and ten worlds.