Subscriber Identity Module (SIM), commonly referred to as a SIM card, functions as a tinny smart card that stores all the necessary data about an individual's network service.

At its core, SIM card works as a copyright to accessing a telecom network, enabling users to send and receive calls. Furthermore, it similarly helps in keeping vital contacts, text messages, and even network-specific data.

There are commonly three types of SIM cards present in the telecom market: the standard size, micro size, and nano. All these variants vary in size, but generate equivalent capabilities.

Every SIM card is characterized by an individual International Mobile Subscriber Identity (IMSI) number, which is consists of a 15-digit numeric sequence. This identifies every individual within the network.

Moreover, every SIM card is programmed with an individual Authentication Key (Ki), which sim information serves for guaranteeing data exchange over the network.

Moving to SIM cards' role, they store details like a user's phone number, service information, and security-related information. Apart from this, they allow additional services including call diverting, call holding, and voicemail.

In conclusion, we see that SIM cards are essential elements of our mobile phones. They act like the IDs for our phones, allowing them work correctly. Knowing your SIM information helps in tackling issues related to your network service.

Additionally, being knowledgeable about your SIM card may also help in facilitating choices about phone upgrades, changing network service, and even traveling internationally.