# 

## Concepts

### Account-Hierarchy

- [About clients and resellers](/docs/concepts/account-hierarchy/clients-and-resellers)
- [About users and roles](/docs/concepts/account-hierarchy/users-and-roles)


### Api-Fundamentals

- [Error handling](/docs/concepts/api-fundamentals/error-handling)
- [AboutReefpay APIs](/docs/concepts/api-fundamentals/intro)
- [Request and response structure](/docs/concepts/api-fundamentals/request-response-structure)
- [About RESTful design](/docs/concepts/api-fundamentals/restful-design)


### Payment-Industry

- [About the evolution of payments](/docs/concepts/payment-industry/evolution)
- [About electronic payments](/docs/concepts/payment-industry/intro)
- [About card networks and interchange](/docs/concepts/payment-industry/networks-and-interchange)
- [About the role of gateways](/docs/concepts/payment-industry/role-of-gateways)


### Security-Compliance

- [About data protection](/docs/concepts/security-compliance/data-protection)
- [About fraud prevention](/docs/concepts/security-compliance/fraud-protection)
- [About PCI-DSS compliance](/docs/concepts/security-compliance/pci-dss-overview)


### Tokenization

- [About stored payment methods](/docs/concepts/tokenization/stored-payment-methods)
- [About tokenization](/docs/concepts/tokenization/what-is-tokenization)


### Transactions

- [About ACH/bank account payments](/docs/concepts/transactions/ach-accounts)
- [About batch settlement](/docs/concepts/transactions/batch-settlement)
- [About cancels and refunds](/docs/concepts/transactions/cancels-and-refunds)
- [About sale vs. authorization](/docs/concepts/transactions/sale-vs-auth)
- [About the transaction lifecycle](/docs/concepts/transactions/transaction-lifecycle)