The relays enable transit across the galaxy from one end to another in relatively quick manner. In truth however, the massive breadth of the Milky Way still remains unknown to civilizations inhabiting it. For example, Citadel Council space is drawn on maps to hold sway over half of the galaxy, while less than 1% of all the stars within that area are explored.
Civilizations have risen in tiny bubbles that have formed around active primary and secondary relays, forming webs of explored and inhabited space. Many concepts and manners have been formulated to define the extent and borders of space relating to the relays.
Kopernei Kalumpo's four-tier Relay Space Classification System is one of the models used at present by Citadel Space governments to define their holdings.
Primary Relay Space
The primary relays are critical junctions and crossroads in modern galactic society. Their unparallered range connects distant regions over thousands of light-years into cohesive and interacting societies that form the Milky Way as we know it.
Whoever owns a primary relay is supreme in their home cluster and galactic power, with authority to control who and what can move in and out of the cluster. The Citadel Council's member states - Salarian Union, Asari Republics, Turian Hierarchy and human Systems Alliance are examples of powers like these.
States and entities in a primary relay's proximity have economic access to resources and trade near other primary relays, as these are available faster than intra-cluster resources. As such, situations can arise where it is cheaper and faster to order products in bulk from another galactic arm rather than ship it from within the cluster.
Outer Primary Relay Space
Worlds and states that have about equal distance to the secondary and primary relay space are in this category. Their economies are still tied to the primary relay's reach, but intra-cluster and secondary relay network's resources play more a prominent role for these worlds.
Secondary Relay Space
Secondary relay networks are formed by smaller mass relays that possess capability to connect to any other secondary relay in their 200-light year range, forming a foam-like map where slow-boating with FTL and taking a secondary relay to the destination compete in economy. They are the proverbial backwaters of clusters.
Secondary relays usually stretch out from primary relay space, but there are few known examples of expanses where slow-boating by FTL is required to reach another secondary network within a cluster. The Nubian Expanse is a recent and unique example of a secondary supercluster, created by the task force responsible for repairing the relays.
Economies of worlds in secondary relay space are more reliant on each other and detached from demand and supply of primary relay space. Only a good reward would make it worth to haul resources and produce from months' worth of distance into the galaxy at large. Empires and states rise and fall in this region of space without disturbing matters outside the cluster.
Beyond secondary relays and their reach is deep space that is only reachable by FTL transit. Deep space is a vast unknown expanse, only touched by telescopes and long-range ships. Tight conventions around activation of relays prevent effective exploration of these regions, leaving it to rogue states and emerging civilizations experimenting with relays to establish new connections.
No prominent state is known to exist in deep space. However persistent rumours in the batarian Confederacy speak of Hegemony remnants who fled Reapers into deep space, and remain there even today plotting their return into wider society.