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If you’re in the market for a new smartphone or carrier — or you’re simply interested in cell phone networks — you’ve likely encountered the acronyms CDMA and GSM before. You may be wondering what they are, and how they affect your phone?

More: What’s the difference between 4G and LTE?

The two cellular standards function in different regions and allow for global communication between individuals, though, each converts incoming and outgoing data into radio waves differently. Neither should be a huge factor when buying a cell phone, but one standard is notorious for tethering you to a carrier while the other is not. It all depends on where you are and what you’re looking for.

GSM explained

The iPhone 7 is a smartphone that typically functions on a GSM network.

GSM stands for Global System for Mobile Communication, and unless you live in the United States or Russia, this is probably the technology your phone network uses, given it’s the standard system for most of the world. GSM networks use TDMA, which stands for Time Division Multiple Access. TDMA works by assigning time slots to multiple conversation streams, alternating them in sequence and switching between each conversation in very short intervals. During these intervals, phones can transmit their information. In order for the network to know which users are connected to the network, each phone uses a subscriber identification module card, or SIM card.

SIM cards are one of the key features of GSM networks. They house your service subscription, network identification, and address book information. The cards are also used to assign time slots to the phone conversation, and moreover, they tell the network what services you have access to. They store your address book, too, along with relative contact information. They can even be used to pass information between phones, if a carrier allows it.

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