Every SIM stores a profile that associates it with a specific cellular network operator which gives access to the provider's network and the networks of any operators they have roaming agreements with. When a device attempts to connect to a cellular network, the operator authenticates the SIM, checking whether the “subscriber” (you) is authorized to use the network. If your device crosses a border or gets deployed in a new country, the multi-carrier SIM attaches to a local carrier it’s authorized to access. Some SIMs, like emnify’s, can also leverage advanced cellular technology like Multi-IMSI and eUICC to access more networks and change carriers in more situations.
IoT SIMs usually come with a web-based platform for remote SIM and connectivity management. They come in multiple form factors like the industrial-grade or MFF2 for durability against extreme environments – heat, corrosion, vibration.Check out our detailed article on the differences between a consumer SIM and an IoT M2M SIM.