Cellular phones have become one of society's most ubiquitous accessories. What was once the domain of the wealthy technophile is now found in nearly every pocket or handbag from pre-teens to the elderly. For many, the cellular phone has even replaced the landline phone as their only telephone service. Yet with so many people purchasing cellular phones it is amazing that so few people know what they are really buying.

Although you may have purchased your phone from a service provider, in many ways the phone is not entirely yours. Many cellular phones are not able to be used at any place or with any carrier you choose. Instead, many cellular phones are locked by the manufacturer, and you can only use certain service providers with that particular phone. That holds true for all phones, unless you have purchased an unlocked cellular phone.

Inside your cellular phone is something called a Subscriber Identity Module, or as it is more commonly known, a SIM card. The SIM card is the key to your cellular phone, and all of your phones identifying characteristics and memory functions are stored there; you might call it the brains and DNA of your phone. The SIM card can be switched from one phone to another, and it allows you to instantly activate your new phone on the network while eliminating the need to reprogram information like your contact list on your new phone.

However, despite all the freedom that the SIM card provides, it is only useful to phones that are programmed to accept certain, preprogrammed SIM cards. Consequently, your phone can only be used in selected places and on selected networks. Only an unlocked cellular phone has the capability to avoid these locks and offer true freedom of service to the owner of the phone.

When most people purchase a cellular phone from a service provider they do not realize that they phone they have purchased is almost always fitted with a network provider lock. That means that no matter how much you like that particular phone, you will not be able to use it with a SIM card from a competing provider network, or even in a country where your provider does not offer service. Further, your phone is probably programmed with features that are inherent to your provider, and therefore even if you were able to switch networks, you wouldn't be able to enjoy many of the features that the phone had previously.

Therefore, even if your cellular phone provider "unlocks" your handset and allows you to use a new SIM card (which they will reluctantly do if certain criteria are met), many of the features you once enjoyed may no longer work. By purchasing an unlocked cellular phone you can avoid those pitfalls and enjoy flexibility that is otherwise impossible.

When you purchase an unlocked cellular phone you do not go through a typical cellular phone dealer (where the phone and service are purchased together). Instead you purchase the phone without a contract, and as long as that phone is unlocked then you can use it with any SIM Card from your previous phones, regardless of the manufacturer or provider you had previously used. Purchasing an unlocked cellular phone without a contract is usually more expensive than buying a similar locked phone with a contract from a service provider. However, the difference in price can be offset if you are an individual with a need to use different SIM cards on your phone.

For example, many phones are locked so that they will only accept domestic SIM cards, so international travel can leave you without a network. An unlocked cellular phone can use SIM cards from the country you are visiting, and this can save you money because connecting to a foreign network can be considerably less expensive when using a SIM card from that country. Domestic providers often charge exorbitant rates on foreign calls, so travelers who have high call volume when abroad can save hundreds of dollars by using an unlocked cellular phone and a foreign SIM card.

You cannot purchase an unlocked cellular phone from conventional network dealers, but if you shop at electronics stores, or from online vendors, you can find all the most popular cellular phone models that the network providers carry, and more, but without the locking restrictions that the networks imbed in their products. For those who travel and can benefit from access to many networks, an unlocked cellular phone is a very logical choice.