Subscriber Identity Module, popularly known as a SIM card, functions as a tinny smart card that holds essential information related to the user's subscription.

In essence, SIM card functions as a copyright to accessing a telecom network, enabling consumers to send and receive calls. Furthermore, it equally helps in retaining important contacts, messages, and even data specific to the network.

There are commonly three kinds of SIM cards available in the market: standard, micro size, and nano. All these versions differ in physical dimensions, but generate the same functionality.

Each SIM card comes characterized by a unique IMSI number, which is comprised of a 15-digit numeric code. This distincts each user within the cellular network.

Moreover, every SIM card is programmed with unique Ki (Authentication Key), which is used for guaranteeing data exchange over the service provider's network.

Switching to the SIM cards' role, they hold details such as your contacts, service information, and security-related information. Apart from these, they allow additional services including call forwarding, call barring, and voice messages.

In summary, it becomes evident that SIM cards are essential elements of our mobile communication. They act like the identity proofs for our phones, helping them operate correctly. Knowing your SIM information helps in resolving any issues related sim information to your network service.

Moreover, having knowledge about your SIM card may also help in making decisions regarding upgrading your phone, moving network service, and even in some cases travelling abroad.