# Concepts


Start with the one-paragraph definition in [What cairn is](/cairn/concepts/what-cairn-is);
from there the section moves out to the graph and the three nouns you write, then
to how plans and the current pointer move over that graph, and finally to the
event log and capability boundary underneath it all.

These pages are for the person who wants to understand how cairn works before
trusting it with a plan; they explain, they do not instruct. When you want to run
the loop yourself, go to the [Quickstart](/cairn/get-started); for exact values, go
to [Reference](/cairn/reference).

- [What cairn is](/cairn/concepts/what-cairn-is) — continuity for agents, the
  stones that name a route, and why the plan lives outside the conversation.
- [The task graph](/cairn/concepts/the-task-graph) — the two stores: a typed-edge
  graph of slug-addressed tasks, and a full-text index of observations.
- [Tasks, observations, and handoffs](/cairn/concepts/tasks-observations-handoffs) —
  the three nouns you write, and the events each one records.
- [Plans, phases, and the frontier](/cairn/concepts/plans-phases-and-the-frontier) —
  why a plan is a task DAG, not a markdown file, and how the frontier finds ready work.
- [The current-task pointer](/cairn/concepts/the-current-task-pointer) — the
  per-session slug cairn resolves slugless writes against, and what moves it.
- [Events, projection, and reconcile](/cairn/concepts/events-projection-and-reconcile) —
  why every write is an event in a durable log, and the database a rebuildable cache.
- [Reads, writes, and capabilities](/cairn/concepts/reads-writes-and-capabilities) —
  how the read/write/observe boundary is drawn by capability, not by tool name.
- [The cairn-method](/cairn/concepts/the-cairn-method) — the loop, the heartbeat
  writes, and the discipline an agent uses to leave work a next session can resume.

The order is dependency order: each page names a thing the pages below it lean on,
so reading top to bottom never asks you to take a term on faith.