It is a standard set of commands allowing the Subscriber Identity Module (SIM) to initiate actions on a mobile phone. Functionality can encompass menu creation, sending SMS messages, and initiating phone calls. A user might interact with it through a SIM menu, for example, to access mobile banking services or to check their prepaid balance directly without dialing a specific code.
This technology enhances the functionality of the SIM card, enabling mobile network operators to offer value-added services directly to subscribers. Its utility resides in enabling secure and convenient access to services directly from the SIM, often in environments where data connectivity is limited or unavailable. Historically, it provided a crucial method for deploying interactive services on feature phones and continues to play a role in emerging markets with limited smartphone penetration.