> For the complete documentation index, see [llms.txt](https://docs.maibmerchants.md/checkout/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.maibmerchants.md/checkout/api-reference/glossary.md). # Glossary Glossary of the main business and functional terms used in **Checkout API** documentation. ***

Term	Description
Checkout	A payment session created by the merchant to collect money for an order. Includes order, payer, and payment data representing the full payment process.
Merchant	A registered business entity authorized to accept payments through maib’s acquiring system.
Terminal	The merchant’s point of sale or integration endpoint through which transactions are processed.
Order	The purchase or service request initiated by the customer and represented in the checkout process.
Payer	The customer who performs the payment using one of the available payment methods.
Payment Method	The channel used to make a payment (e.g., MIA QR, Card, Apple Pay, A2A).
Refund	The process of returning funds for a completed payment due to a cancellation or return.
Callback	A system notification sent by maib to the merchant’s server containing the final payment result.
Sandbox	The testing environment that simulates transactions without real payments.
Status	Indicates the current state of the payment or checkout (Created, WaitingForPayment, Completed, Cancelled, Refunded).
Signature	A digital verification hash confirming the authenticity of callback notifications.