---
page_source: https://juspay.io/in/docs/upi-plugin-direct-psp/android/overview/introduction
page_title: Introduction
---


# Introduction



Welcome to the **UPI Plugin Direct PSP Integration**  Document. This doc consists of the comprehensive information about our **Plugin SDK & Backend S2S APIs** . We use **application/json**  content type for our request and response.

This documentation is designed to guide you on step-by-step flow, everything you need is outlined in the sections below. Before you dive into the SDK-Calls/APIs, we recommend familiarizing yourself with the Request and Response structure. This will provide you with essential insights into prerequisites and overall formatting, ensuring a smooth integration process.

**The docs covers different use cases of a merchant for payments processing** **:** 

* 1st **[Transactions](https://docs.juspay.in/upi-merchant-stack/docs/transactions)** **(Payins & Refunds)**  where merchants want to acquire/collect money from user on **demand basis** for one-time payments & refund against original transaction.
* 2nd **[Mandates](https://docs.juspay.in/upi-merchant-stack/docs/mandates)** **(UPI AUTOPAY)**  where merchants want to acquire/collect money from user on **regular basis**  for recurring payments by one-time mandate creation(registration). This would mostly be used for Subscriptions, Bill Payments, Investments, Insurance Payments, Donations, Wallet Top-ups etc.