> ## Documentation Index
> Fetch the complete documentation index at: https://docs.atum.xyz/llms.txt
> Use this file to discover all available pages before exploring further.

# Core concepts

> Key ideas to understand before you integrate — browse by topic below.

These pages explain the vocabulary and boundaries you need before calling the Payment Gateway. For the end-to-end flow, start with [Atum payment lifecycle](/get-started/overview/how-an-atum-payment-works).

<Note>
  New to tokenized currency payments? Read [Atum infrastructure](/get-started/architecture/payment-rails-primer) first.
</Note>

## Browse by topic

| Topic                                                              | What you'll learn                                                                        |
| ------------------------------------------------------------------ | ---------------------------------------------------------------------------------------- |
| [What is Atum ID?](/get-started/identity/overview)                 | How identity credentials travel with a payment, separate from authorization              |
| [Know Your Agent](/get-started/identity/know-your-agent)           | Who is answerable when software spends on your behalf                                    |
| [Payment request](/get-started/concepts/payment-intent)            | What you submit and what happens next                                                    |
| [Policy enforcement](/get-started/concepts/policy-enforcement)     | Who may fulfill a payment — identity lists you set vs credential-type trust Atum applies |
| [Network participants](/get-started/concepts/participants)         | Who does what in a payment                                                               |
| [Corridors and assets](/get-started/concepts/corridors-and-assets) | Which rail and token pairs are supported                                                 |
| [Token approvals](/get-started/concepts/permit2-and-approvals)     | One-time setup before your first payment                                                 |
| [Idempotency](/payment-protocols/idempotency)                      | What to do when a payment is still settling                                              |

Full alphabetical index: [Glossary](/get-started/reference/glossary).