What does regulated investment company mean?

A US registered investment company that must (a) provide its shareholders voting rights in proportion to their ownership interest, (b) derive at least 90% of its dividends and interest from a portfolio of certain assets that is maintained at a required level of diversification, and (c) periodically distribute at least 90% of its income to its shareholders, in order to avoid the taxation of the income at the corporate level – the distributed income is instead taxed as ordinary income at the investor level.