The unified payments interface or the UPI is an interface via which you can transfer money between bank accounts across a single window. This means you can send or receive money or scan a quick response (QR) code to pay an individual, a merchant or a service provider to shop, pay bills or authorise payments.
To enable payment using your phone, all you need is a mobile payment application and the virtual address of the payee (that reads something like [email protected]). This implies you can make payments directly to the accounts of a vendor or a person, in one step. There is no repetitive step involved. For example, entering bank details or other sensitive information each time you need to make a payment.