Razorpay

1. Payment Gateway overview

   Payment flow of orders, checkout, payment capture and verification.

2. API authentication

   Key ID and key secret, test versus live mode.

3. Orders API

   Creating orders before payment and linking payments to them.

4. Standard Checkout

   Web checkout integration and signature verification.

5. Payments and capture

   Payment states, authorized versus captured, auto-capture.

6. Refunds

   Instant and normal refunds and statuses.

7. Webhooks

   Event delivery, signature validation and retries.

8. Subscriptions

   Plans, subscriptions and recurring charges.

9. Settlements

   Settlement cycles and reconciliation.

10. Disputes and chargebacks

    The Disputes API for chargebacks and evidence.

11. Payment Links

    Collecting payments through Payment Links.

12. Testing

    Test card details for payments.

13. Errors

    Error codes and troubleshooting.

Each section links to the official page. Titles and summaries by Extra Credit; the docs belong to their authors.