From what I can surmise, using it allows them to traverse others' dreams and alter them at will--and it allows the rest of us to move freely between dreams, as though all of our minds are connected. However, it is much more difficult to imitate the ability while dreaming, as we are all technically unconscious. But I have been practicing... and at least in my own dream, I have learned how to alter things at will. But it is challenging.

Being aware of it, however, has helped me change it when I do dream.