A payment gateway is the software interface through which a merchant or application sends and receives payment information to and from payment-processing infrastructure.
For stablecoin payments, a gateway can generate addresses or payment requests, display token and network choices, return transaction status, and connect the merchant's checkout to a processor, wallet, exchange, or blockchain service. A gateway can be bundled with processing services, but the interface function remains conceptually separate from transaction execution and settlement.
The gateway is the merchant-facing technical interface. The processor performs or coordinates the underlying processing, monitoring, conversion, or settlement functions.
Separating gateway and processing functions helps describe where checkout integration ends and where payment execution, risk management, and settlement begin.
An e-commerce checkout can call a gateway API to request a USDC invoice and receive a payment address and status updates.