> For the complete index of the 402pay docs, see [llms.txt](https://developer.402pay.co/llms.txt).

# Glossary

The terms the API and these docs use, from actor to webhook endpoint.

The words these docs and the API use, in one place. Each one links to the page that covers it in full.

## A

- **Actor**:  Who caused an event: `user` for a person in the dashboard, `api_key`, `customer` at checkout, or `system` for 402pay itself, such as a payment confirming. See [event fields](https://developer.402pay.co/guides/webhooks.md#event-fields).
- **API payment**:  A payment your server creates with `POST /payments`, for an exact amount, with your `reference` and `metadata` and a hosted checkout of its own. Every checkout opened on it is one attempt at the same payment. See [accept a payment](https://developer.402pay.co/guides/accept-a-payment.md).

## B

- **Business**:  One merchant account, with its own wallet, keys, payments and settings. One person can own several, and a secret key acts as exactly one. IDs start with `biz_`. See [core concepts](https://developer.402pay.co/concepts.md#businesses).

## C

- **Checkout**:  One attempt to pay a payment or link, in one rail, coin and network. A crypto checkout reserves a fresh address in your wallet and locks a quote. IDs start with `chk_`. See [hosted checkout](https://developer.402pay.co/guides/hosted-checkout.md).
- **Checkout address**:  The fresh address in your wallet that one crypto checkout pays to, so every transfer matches one payment. Every EVM network shares it. See [wallet and deposits](https://developer.402pay.co/guides/settlement.md).
- **Confirmation**:  A block added on top of the one holding a transfer. Each network needs a set number before a payment succeeds. See [supported networks](https://developer.402pay.co/guides/networks.md).
- **Customer**:  A person grouped by email, with their payment count and totals, added as soon as checkout has their email. You can block one from paying. IDs start with `cst_`. See [list customers](https://developer.402pay.co/api/customers/list.md).

## D

- **Deposit**:  Where a paid payment's funds landed: a wallet transaction into your wallet, in the coin and network paid, for the whole amount that arrived. The payment's `settlement` field shows it, or that the payment was collected as fees instead. See [wallet and deposits](https://developer.402pay.co/guides/settlement.md).

## E

- **Event**:  A record of something that happened, such as `payment.succeeded`, with a snapshot of its subject as it was then. Webhooks deliver events. IDs start with `evt_`. See [list events](https://developer.402pay.co/api/events/list.md).
- **External wallet**:  A wallet you already use, connected by its public keys, so 402pay never sees its recovery phrase. Payments land in it, and sends happen in its own app. See [wallet and deposits](https://developer.402pay.co/guides/settlement.md).

## F

- **Fee statement**:  What your business owes 402pay in fees, and the entries behind it. Once you owe enough, 402pay collects it by sending whole payments to its own address, whose `settlement.destination` is `fees`. Entry IDs start with `fee_`. See [fees and billing](https://developer.402pay.co/guides/fees.md).

## I

- **Idempotency key**:  A random value sent in a header that makes a POST safe to retry: the same key returns the first response instead of doing the work twice. See [idempotency](https://developer.402pay.co/api/idempotency.md).

## M

- **Main address**:  The first address on each network in your wallet, the one to share for deposits. Sends draw on whichever of the wallet's addresses hold the coin, largest first.
- **Metadata**:  Your own key-value strings on a payment, returned with it and with every event about it. See [metadata](https://developer.402pay.co/api/metadata.md).
- **Mode**:  `test` or `live`, for the kind of key behind an event. Always `live` during the beta, when test and live keys share data. See [test and live keys](https://developer.402pay.co/testing.md#test-and-live).

## P

- **Payment link**:  A reusable hosted checkout with a fixed price. Every customer who pays it makes a new payment that carries its `link_id`. IDs start with `lnk_`. See [payment links](https://developer.402pay.co/guides/payment-links.md).

## Q

- **Quote**:  The coin amount a crypto checkout asks for, at a rate locked for a window, 15 minutes by default. A transfer after it expires needs your review. See [underpayments and overpayments](https://developer.402pay.co/guides/underpayments.md).

## R

- **Rail**:  How the customer pays: `crypto` or `card`. Card payments arrive in the coin and network selected for that checkout. See [card payments](https://developer.402pay.co/guides/card-payments.md).
- **Reference**:  Your own ID for an API payment, such as an order number. It names one live payment, so a retried create returns the payment that already exists. See [create the payment](https://developer.402pay.co/guides/accept-a-payment.md#create-the-payment).
- **Remainder**:  A checkout for exactly what's left of an underpaid payment, in the same coin and network and attached to the same payment, so no second payment is made. See [request the rest](https://developer.402pay.co/guides/underpayments.md#request-the-rest).
- **Request ID**:  The `req_` ID in every response's `402pay-Request-Id` header, repeated in every error as `request_id`. Include it when you contact support.
- **Restricted key**:  A secret key with none, read or write on each resource, rather than full access. See [restricted keys](https://developer.402pay.co/authentication.md#restricted-keys).
- **Review reason**:  Why a checkout's funds need your decision: `late`, `wrong_network` or `claimed`. It's on the checkout, in `review_reason`. See [needs review](https://developer.402pay.co/guides/underpayments.md#needs-review).

## T

- **Tolerance**:  How far short a crypto transfer can fall and still count as paid in full, 0.5% unless you change it in Settings, under Checkout. See [underpaid](https://developer.402pay.co/guides/underpayments.md#underpaid).

## W

- **Webhook endpoint**:  A URL on your server that receives signed events of the types you choose, retried until it answers. IDs start with `whk_`. See [webhooks](https://developer.402pay.co/guides/webhooks.md).