The Subscriber Identity Module (SIM) Application Toolkit is a standard which allows the SIM card to initiate actions which can be used for a variety of value-added services. It comprises a set of commands programmed into the SIM which define how it interacts with a mobile device and network. An example of its application is in mobile banking, where the SIM card houses secure applets that enable financial transactions directly from the phone.
Its significance lies in providing a secure and authenticated channel for mobile services, offering benefits such as enhanced security features, user convenience, and the ability to operate independently of the mobile operating system. Historically, it emerged as a method for mobile operators to deliver their services and manage SIM card behavior before widespread smartphone adoption and app ecosystems.