The term payment gateway originates primarily from the areas of eCommerce and digital commerce as well as crowdfunding and finance. A payment gateway is a technical service that ensures that online payments can be processed securely and smoothly. When someone makes a purchase in an online shop and pays by credit card, PayPal or other digital payment methods, a payment gateway is almost always used.
The payment gateway works like a digital "middleman". It receives the buyer's payment data, checks whether the data is correct and whether there is enough money in the account, and then forwards the payment to the seller's bank. The payment gateway is active in the background for customers, who usually don't notice it.
An illustrative example: Anna orders a pair of shoes in an online shop and wants to pay with her credit card. The payment gateway checks her card details at lightning speed and forwards the payment. If everything is OK, Anna immediately receives a confirmation and the retailer receives the money.
Secure and fast online payments would hardly be possible without a payment gateway - it is an important building block for success in digital commerce.