Planespace

Planespace was the term that broadly speaking, referred to anywhere beyond Toril on the Material Plane (i.e. within and beyond the Seiros system) and on another plane. Skipjammer ships could weave through it effectively as they could traverse space, and skip planes too. Skipjammers often used planar portals to weave through Planespace instead, as it was less costly in terms of fuel and didn't require attuned forks.
 It's important to note that the vast majority of people on Toril had no idea that anything beyond themselves existed.
A planar portal could take many forms - a rift, a wormhole, a black hole, a tear in space time, flying off the edge of the map or even into a star. It could be in planespace alone, on a planet, as an anomaly, or other potential places.
Overlap of planes allowed travel between them, and planes that did not overlap could not be travelled between. The only exception was Sigil, which could be visited from any location without a tuning fork. 
The Ethereal Plane bordered all the Inner Planes, including the Prime Material. The Astral Sea bordered all the Outer Planes. They also both bordered one another, and you could freely move between the two of them via the Border Ethereal. As such, if you wanted to travel from the Material to, say, Mechanus, your route would be Material -> Ethereal -> Border Ethereal -> Astral -> Mechanus. 
The plane of Elemental Chaos bordered both the Ethereal and Astral. It was not necessary to travel through, though (thankfully). 
The Material Plane was at the centre of Planespace. It was bordered by the Feywild and Shadowfell (the latter causing the blurring phenomena known as the Underdark effect). They bordered the Ethereal, which itself was part of the plane of Chaos. Chaos was connected to the four main elemental planes and all their sub-planes, like the planes of ice, wind, snow and more. The outer planes also had infinitely more planes than were shown on the diagram.
Category:Planes
Category:Space