What Is a GSM SIM Card?
A Global System for Mobile Communication Subscriber Identity Module, or GSM SIM card, is a SIM card that uses the GSM network. Having this card in an unlocked cell phone while using the correct frequency allows a cell phone user to use his cell phone in various countries all over the world. The GSM network is the network used by most countries in the world, allowing cell phone users to carry their phones from country to country. This network is not the primary network used in countries such as the United States, which is why many US residents have trouble using their phones overseas.
