You can search on here...and get some info, as well as on the widow wall.
In a nutshell, it has a more pronounced palm swell, and the thumb relief cutout on the right side of the bow (as you draw it, assuming you're right-handed), is lower, supposedly forcing your thumb lower.
This is supposed to exert a different pressure on your hand/grip form, in order to allow a more natural "pointing" aspect to the bow when it is canted.
I have also read the grip is "higher" than the standard grip, but I am not sold on that yet, and G. Fred did not say that in his description about the grip on the widow wall.
That said, the PMA I have coming has the Asbell grip...
Take Care,
Marc