SIM
The secure chip or card that identifies a device on a mobile network and holds the operator's credentials.
A SIM stores the subscriber identity and keys that let a device join a network. IoT SIMs come in industrial grades that survive heat, cold and vibration, in removable or soldered formats.
Why it matters for business
The SIM ties a device to an operator and its tariffs. How you can change that link later (by swapping cards or remotely) is a key long-term cost and risk decision.