A payment gateway enables a connection between a website and a bank which allows the instantaneous transfer of funds into an account. This is usually for the payment of goods or services to a website, or to transfer funds between bank accounts (employers etc.). It is in real-time.
It provides a secure connection between a customer, a bank, and the website (company), through the use of an SSL certificate. The bank communicates whether the transfer of funds between the customer and the website was successful.