payment gateway
A payment gateway is the software layer that collects payment details from a website, app or terminal, encrypts them and sends them to the acquirer and card scheme for authorisation, returning the result. It carries the message, not the money. Many providers bundle gateway and acquiring together.
The gateway is the part of payments a developer actually touches: the SDK or API that takes a card number, a wallet or a stored token, applies 3-D Secure where needed, and returns approved or declined. Historically it was sold separately from acquiring, with a per-transaction gateway fee on top of the merchant service charge. Most providers now bundle both, which is cleaner but makes the gateway fee invisible on the bill.
Why it matters to a software platform: the gateway is where the platform's product meets the payment, so its design decides how much of the checkout the platform controls. A hosted page is quick to adopt and lets the regulated party own the card data entirely; an embedded component gives the platform the look and the flow while keeping card data out of its own servers; a fully custom integration puts the platform in PCI scope. A platform's developer makes that choice and builds against the SDK and documentation; a named payments engineer at Synapto answers questions while they do.
What to watch: a gateway contract separate from acquiring can mean two contracts to leave when a business switches, and tokens held in one provider's gateway do not move freely to another. Ask who owns the token vault before signing.