An online payment gateway is a technology that facilitates the transfer of payment information between a customer and a merchant. It acts as a bridge, securely processing credit card and other payment transactions over the internet. When a customer makes a purchase, the gateway encrypts their payment details and sends them to the payment processor for authorization. These gateways are essential for e-commerce businesses, as they ensure that transactions are completed safely and efficiently. Popular examples of payment gateways include PayPal, Stripe, and Square. By using these services, merchants can accept payments from customers around the world with ease.