# Terminology
**Name** **Description**
Customer Institution which is using Verestro products. This institution decides which SDK should be used and how transaction should be processed. Basicly Customer can be called Verestro client.
User User which is using Payment Hub Application. It is root of entity tree. User is identified in Wallet Server by some unique identifier which is provided after registration. User can have access to his data and operations based on session. User’s session is created after device pairing is performed. When session expires then user authentication have to be performed. Session is valid 10 minutes, however it is configurable parameter.
Card Card belongs to the user. User can have many cards. Card is identified via internal id given after storing card on Wallet Server. Whole PAN is stored on Wallet Server which has PCI DSS certificate.
Device Device belongs to user. When user starts using application after installation then device pairing is performed. After pairing device with some unique id, unique device installation id is generated and this installation is assigned to user. It is possible to have one active installation on specific device for specific user.
Session Token Token which defines User. It is an authorization way of the User. This entity is created after paring device and this is needed to perform any actions in the application. When session is expired then user authentication needs to be performed. Session is valid 10 minute s, however it is configurable parameter.
Sender Verestro Wallet user which triggers transaction to the Receiver (check User description).
Receiver Receiver can be identified in Wallet Server (Internal) or may be an entity that does not exist in Wallet Server (External). ◦ Internal – this type of Receiver has his own unique identifier just like sender. It can also act as a Sender in the transaction process. ◦ External – this type of Receiver does not exist in Wallet Server. Transfers that are made to this type of Receiver require the entering of his card data by Sender.
Mid Merchant identifier. This entity is representing Merchant in Acquirer’s system. Customer have to provide the mid information to enable mid configuration in the Verestro system. Required to process 3DS authentication via Verestro System.
Acquirer External institution responsible for processing transaction and 3ds requests ordered by the Verestro Payment Hub App. Acquirer connects with banks / card issuers and returns information whether the ordered action on a given card is possible.
PAN (Primary Account Number) It is 14-19 (usually 16) digits number which is a unique identifier of the payment card issued to the customer's account.
Wallet Server Provides the backend services to support Mobile Payment Application via Verestro Wallet SDK and is responsible for managing users, devices, cards , device tokens, storing transactions history and communication with Acquirers.
PCI DSS PCI DSS (Payment Card Industry Data Security Standard) is a security standard used in environments where the data of payment cardholders is processed. The standard covers meticulous data processing control and protection of users against violations.
IBAN IBAN (International Bank Account Number) is an international standard for bank account numbering that allows you to transfer funds to foreign accounts and to receive transfers from foreign entities to domestic bank accounts. One of the assumptions of the IBAN standard is to simplify the system of cross-border transfers.
QR A QR code (quick response code) is a two-dimensional barcode. [Check here for more details.](https://en.wikipedia.org/wiki/QR_code)