Short answer. A Domain is a sovereign economy governed by its licensee. A Hub is a settlement hub that connects domains and clears between them. An Annex is a single-asset gateway, such as a gold annex or an oil annex. Every Domain, Hub and Annex uses the JIL Layer-1 rail.
A Domain was called a Class A in earlier drafts. The words Domain, Hub and Annex are the names now.
Domains and Hubs settle across the federation through corridors, and a corridor transfer pays the toll in the 100-point waterfall. Inside one chartered domain a non-commercial transfer pays 0 basis points.
The live demonstrations are on demo.jilsovereign.net: Nubara and Tirmore as two domains, a gold and an oil annex, the Ignition Switch exchange, and the L1 application and record. A pilot studio is at pilot.jilsovereign.net. They run on demonstration data. To license a Domain or a Hub, request a briefing.