can someone explain the process. thanks in advance. answers are greatly appreciated.

private int NegaMax(int p) {
        int End = GameOver();
        if (End != 0)
            return End;

        int best_value = (p == 1) ? 512 : 2048;
        for (int b = 1; b <= 256; b = b << 1) {
            int move = (~(X | O) & b);
            if (move != 0) {
                put(p * move);
                int s = NegaMax(-p);
                best_value = p * (s & 0xfffffe00) > p
                        * (best_value & 0xfffffe00) ? ((s & 0xfffffe00) | move)
                        : best_value;
                clear(move);
            }

        }
        return best_value;
    }