The Inner Bleed:
The Inner Bleed is comprised of fairly thin roads that form a buffer between the planes and demi planes. It has been suggested that this was originally just a buffer to prevent the planes touching. However as the universe has developed, the Bleed has become a plane of its own.

The Outer Bleed:
The Outer Bleed was comprised of vast spaces which formed a buffer between realmspaces. After the Geos realmspace was sealed off from the rest of the Universe, the Outer Bleed became the border which surrounds the Geos realmspace.

Planar Lore Notes
Anything which is severed from an individual while in the Bleed and is not replaced before entering a plane is permanently lost and to anyone who was not in the Bleed at the time of the severing the severed item has always been missing and was missing before the individual entered the Bleed. There is a story of a powerful female Planeswalker who entered the Bleed, shaved her legs and returned home, thus preventing the need to ever shave again.