Application Identifier (AID)

Defined within ISO 7816. A data label that differentiates payment systems and products. The card issuer uses the data label to identify an application on the card or terminal. Cards and terminals use AIDs to determine which applications are mutually supported, as both the card and the terminal must support the same AID to initiate a transaction. Both cards and terminals may support multiple AIDs. An AID consists of two components, an RID (alpha and numeric) and a PIX (numeric only).