# Concepts

A retrievability probe is only as useful as the mental model behind
the numbers it prints. The chapters in this section cover the
essential ones:

- [Swarm references vs IPFS CIDs](./swarm-refs.md) — what the 64-hex
  address actually identifies, and why this isn't a CID.
- [The stewardship probe](./stewardship.md) — what `GET /stewardship/{ref}`
  does on the inside, and why it can disagree with a plain `/bzz`
  download.
- [Multi-vantage and "partial"](./multi-vantage.md) — what each row
  in the report represents, and how the top-level status is
  aggregated.
- [Overlay, neighborhood, proximity order](./proximity.md) — the
  geometry of the Swarm address space and how `bee-check` annotates
  each vantage with its position relative to the chunk.
- [Manifests and per-chunk drill-down](./manifests.md) — why a "yes"
  on stewardship sometimes hides per-chunk gaps, and what `--per-chunk`
  exposes.
- [Postage batches and re-seeding](./postage.md) — what a batch is,
  what makes one "usable", and how re-seeding works under the hood.

If you only read three: [Stewardship](./stewardship.md),
[Multi-vantage](./multi-vantage.md), and
[Proximity](./proximity.md).
