Although the first prototype for a cellular system was built in 1977, mobile phones and networking are still making exponential strides in terms of use and features. The SIM card is a perfect example of this. A SIM card increases a cell phone's adaptability, and can benefit cellular users in a number of ways.

SIM stands for Subscriber Identity Module. In essence, a SIM card is a tiny, removable chip inside the cell phone that stores information including the user's phone number, the names and information in the phonebook, and the service plan, as well as other subscriber data. This allows cellular carriers to instantly identify users within the network. SIM cards can be switched freely between compatible phones.

This network, also known as GSM or Global System for Mobile Communications, spans the globe and has taken cellular mobility to the next level of performance. In addition to recovering data from a lost or broken phone, SIM cards, along with the GSM, enable cell usage in other countries. Currently, your cellular plan functions only in your country of residence--travel abroad and you get no service.

Mobile users can purchase SIM cards from other countries. Simply insert the SIM card, and your existing phone connects to that country's cell service provider. SIM cards are even available in pre-paid formats, just like calling cards. This enables users to purchase 50 dollars of cell phone talk-time between England and the U.S., for example, and they can then speak freely until the 50 dollars runs out.