A payment gateway is an ecommerce service that processes credit card payments for online and traditional brick and mortar stores. Payment gateways facilitate these transactions by transferring key information between payment portals such as web-enabled mobile devices/websites and the front end processor/bank. Payment gateways fulfill a vital role in the eCommerce transaction process, authorizing the payment between merchant and customer. Popular payment gateways include PayPal/Brain tree, Stripe, and Square.