1. Business - a retailer or service company, having an online/electronic system.
2. Online Payments Page - an online payments system, that allows you to easily build a payments' module into any type of business.
3. Callback - calling of the service chosen by the business from the banking system to provide updated information on the payment.
4. System Entering Credentials - a client’s identifier in the banking system (`client_id`) and a secret key (`secret_key`), given by the bank to the client upon its successful registration.
5. Card Number (PAN) - 16 digits given on the front side of the bank card.