This guide explains the two types of cell phones; GSM and CDMA, and how to get the right one for you as well as explaining what a World Phone is. 

GSM Cell Phones.  GSM cell phones use a sim card which is a small piece of plastic that you can easily insert and remove from a GSM cell phone.  The sim card has all of your cell phone account information that is used by the cell phone company to keep up with your billing and other account information.  You can also store phone numbers and other infomation on the sim card. 

There are two main cell phone companies in the US that uses GSM (sim card) technology: Cingular Wireless and T Mobile.  There are several other smaller carriers that use them including SunCom, Fido, Rodgers AT&T, and in some areas Cellular One.  As a general rule, you must get a GSM phone that is programmed to the particular cell phone company you use (Cingular or T Mobile for example) unless the phone is "Unlocked".  If the phone is unlocked, you can use it any other US GSM cell phone company (you can put your Cingular sim card in a T Mobile phone that is unlocked and it will work).  For a more detailed explanation of Unlocked cell phones see my guide "Unlocked Cell Phones:  What it Means to be Unlocked".  The rest of the cell phone companies in the US do not use this technology and they use CDMA technology (see CDMA Cell Phones Below).

World Phones (GSM for the World).  Most of the world uses GSM, however, in Europe, Asia, and Africa they use a different frequency that is not used in the United States.  With the start of the Sony Ericsson T28w, it was one of the first James Bond phones, the cell phone carriers started introducing GSM phones that would work on the US standard and the European standard.  These phones are commonly called World phones.  For a more detailed discussion of World Phones, see my guide "World Phones: What do I need for My European Vacation".

CDMA Cell Phones.   CDMA cell phones use the technology developed by Qualcomm.  CDMA cell phones do not use sim cards and your account information is stored in the hardware of the phone.  The US cell phone companies using exclusive CDMA are Verizon, Sprint, Alltel, US Cellular, Metro PCS and Cricket, plus a host of small prepaid phone companies.  CDMA technology is the fastest growing worldwide and is slowly taking market share from the GSM market, even in Europe where GSM is everywhere. 

When you get a CDMA phone it must be programmed to your cell phone carrier.  Unlike GSM phones, CDMA phones can not be unlocked and easily changed from one cell phone company to another.  Thus, if you have Verizon, get a phone that is programmed to Verizon, otherwise, you can not get activated on Verizon.

I hope you found this guide helpful, if so, please click "Yes" in the blue title bar below and thanks for reading.  Check me out on eBay at JustCellular.