A SIM card is short for Subscriber Identity Module card. It
is a tiny card which is fitted into

GSM cell phones at the time of signing on as a subscriber. It holds the details of the subscriber, security data, and memory to store personal numbers. A SIM card stores information which helps the network service provider to recognize the caller. A SIM card is a removable memory card and can be put into any compatible GSM handset or GSM modem, permitting the user to keep the same number while changing handsets. It is a standard unique chip which is a must in every GSM cell phone.