# Concepts

The vocabulary of the network: stations, lines, links, passes, the topology, taps, and what is kept until when.

Liminal is drawn as a rail map because that is what it is: stations that serve, lines that carry, links that join two maps, and a pass checked at every gate.

[Stations and lines](/liminal/concepts/stations-and-lines/)

A service is a station; the subjects it serves and the channels that carry messages are lines.
[Links](/liminal/concepts/links/)

Two liminals joined over an authenticated wire, exports named at configuration, every open checked.
[Passes and placement](/liminal/concepts/passes/)

Lys issues the passes, places the subjects and decides every grant; liminal enforces.
[Taps and the topology](/liminal/concepts/taps/)

What the console draws, what a tap records, and the outcome of every call.
[What is kept](/liminal/concepts/durability/)

Durable until delivered and acknowledged, then pruned. Liminal is not the system of record.