> ## Documentation Index
> Fetch the complete documentation index at: https://docs.revolv3.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Core Concepts & Data Models Overview

> High-level overview of Revolv3 entities: Merchant, Customer, PaymentMethod, Invoice, Attempt, Subscription. Learn how they relate and where to find detailed guides.

This page introduces the main entities in the Revolv3 API and how they fit together. Use it as a map before you read the detailed guides for each concept.

## Entities at a Glance

| Entity            | Role                                                                                                           | Learn more                                                                                                                                                |
| ----------------- | -------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Merchant**      | Your Revolv3 account and its settings (processors, defaults, order channels).                                  | [Merchant Settings](/docs/core-concepts/merchants/merchant-setting), [Order Processing Channels](/docs/core-concepts/merchants/order-processing-channels) |
| **Customer**      | Optional record for a payer; links payments, subscriptions, and payment methods.                               | [Customer](/docs/core-concepts/customer/customer)                                                                                                         |
| **PaymentMethod** | Stored payment credentials (card, ACH, etc.) used to charge a customer.                                        | [Payment Method Guide](/docs/core-concepts/paymentmethod/paymentmethod-guide), [ACH Direct Debit](/docs/core-concepts/paymentmethod/ach-direct-debit)     |
| **Invoice**       | Billing document for a charge; holds amount, line items, and state.                                            | [Invoice Status](/docs/core-concepts/invoice/invoice-status), [Get Invoices API](/docs/core-concepts/invoice/get-invoices-api)                            |
| **Attempt**       | A single try to pay an invoice (e.g. one card charge or one ACH pull). One invoice can have multiple attempts. | [Get Invoice Details](/docs/core-concepts/invoice/get-details-of-invoice-attempts)                                                                        |
| **Subscription**  | Recurring billing plan; creates invoices on a schedule and optionally links to a customer and payment method.  | [Create a Subscription](/docs/core-concepts/subscription/create-subscription), [Billing Plans](/docs/core-concepts/subscription/billing-plans)            |

For status values and enums used across these entities, see [Statuses & enums](/docs/core-concepts/status-enum).