The term Payment Gateway originates primarily from the fields of e-commerce and digital commerce, as well as crowdfunding and finance. A Payment Gateway is a technical service that ensures online payments can be processed securely and smoothly. When someone buys from an online shop and pays using a credit card, PayPal, or other digital payment methods, a Payment Gateway is almost always used.
The payment gateway functions like a digital „intermediary“. It receives the buyer's payment details, checks if the details are correct and if there are sufficient funds in the account, and then forwards the payment to the seller's bank. For customers, the payment gateway operates in the background; they 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.
Without a payment gateway, secure and fast online payments would be hardly possible – it is a vital building block for success in digital commerce.
Deutsch 
English (UK)