A payment gateway is needed for commercial shops or sites that take payment rather than sending money.
Things like PayLine and PayPal are payment gateways, and they are treated as e-wallets even though there is no physical way to withdraw money from them, much less top up from a terminal. It's more of an internal transfer system from where people will withdraw money to a special card, and it has to be ordered. Without a physical card, a person can put money into it temporarily to be able to pay later on a website or in a shop. This is the gateway. It can be used as a transit transaction for example for
chalkkids.co.uk cards or other credit cards. I like the fact that credit card debits can be held in the gateway until they go to the recipient's account. It's a guarantee of my solvency, so such gateways are in principle acceptable in monetary transactions.