A GSM phone is a mobile phone that is powered by the Global System for Mobile Communications. This transmission technology was first introduced to the public in 1991 and has now become the most popular in the world.
Unlike analog phones, GSM allows three voice calls to occur in the same time slot. This is due to a combination of encryption and digital compression technology. GSM also has better security.
GSM phones make use of a SIM (or "Subscriber Identification Module" card). This very small chip, which can be inserted into a phone and removed and placed into another unit, stores important information: contact numbers, calendar information, and personal identification information. This is very handy when one uses two phones or wishes to upgrade to another phone.
GSM is used in Asia and Europe, and has enabled global travelers to use one phone even when visiting other countries. It has also played a role in the surge of text messaging. Because of one standard for different phone companies, it is easy and cheap for users to send text messages to each other, even if they belong to rival networks. This is in stark contrast to the United States, where carriers adopt different technologies and must course text messages through third party gateways.
GSM is slowly gaining ground in the United States, however, due to Cingular Wireless. Now the largest mobile provider in America, this company has begun using GSM technology and promoting its benefits, including the convenience of the SIM card.