Blurring the Lines
The Hogyoku is another one of Kisuke Urahara's inventions from Bleach. The Orb was a device that Urahara made and hid inside of Rukis'a Gigai when she was injured and left her powers inside of Ichigo. The Orb was made to draw power out of a Soul Entity and then contain it. Why exactly Kisuke made the Orb is yet unknown. With the Orb of Distortion a person has the ability to do away with the boundaries of the spiritual entities known as Hollows and Soul Reapers. This ability can make it easier to create Arrancar that are perfect, Like Aizen uses it, and could therefore theoretically be used to create Vizard powers in a Soul Reaper.
Key to the Heavens
Later in the series it is discussed that the Orb can be used with a sacrifice of lives and spirit energy to create a key that will connect the worlds with the way to the King, presumably a god that resides over everything an opposite to the devil that was shown earlier in the series. It is believed that Aizen is only waiting for the right time to get all the people and power together and then using the Orb to open the gates so that he can try and take the throne from the god that is over all.
Even after spending a long time inside of Rukia drawing off her Spirit Pressure the Orb does not gain an infinite ability to create energy with. Once the Orb is out of energy it will be useless until it is refilled again.