The primary function of a payment gateway is to facilitate the online transaction process between customers and merchants. It serves as an intermediary that securely captures and transmits payment information from the customer to the merchant’s bank and returns the transaction response. Payment gateways ensure encryption and compliance with security standards to protect sensitive data like credit card details. They offer various payment options and fraud detection mechanisms, enhancing customer trust. By providing a seamless checkout experience, payment gateways play a crucial role in e-commerce success.