Background, not instructions. You can integrate successfully without reading it, but the vocabulary here turns up in responses and support conversations.
| Party | Does |
|---|---|
| Cardholder | Presents a card |
| Merchant | Sells the thing. Your customer, or you |
| Gateway | Takes an API request and turns it into a processor message. This is us |
| Processor | Connects to the card networks. TSYS, for cards |
| Card network | Visa, Mastercard, Amex, Discover. Routes to the issuer |
| Issuing bank | Holds the cardholder's account and decides approve or decline |
| Acquiring bank | Holds the merchant's account and receives the funds |
You talk to the gateway and nothing else. No direct connection to a processor, a network, or a bank is needed.
A card payment is two events, usually hours apart.
Authorization asks the issuer to reserve funds. It is synchronous — the answer comes back in the API response, and it is where an approval or a decline happens.
Settlement actually moves the money. Transactions gather in a batch, the batch closes on a schedule, and the acquirer funds the merchant a day or two later.
That gap is why is_settled is false on a transaction you just approved, and why a void and a refund are different operations. See Transaction lifecycle.
| One integration | Card and ACH through one API, rather than one per processor |
| Tokenization | A payment token instead of storing card numbers |
| Normalized responses | The same transaction object whichever processor handled it |
| Settlement | Batching and close, with reporting to reconcile against |