We can barely function without these bad boys, but what do we really know about them? When it comes to SIM cards, all we really know is that when we plug it into the device, it allows us to use our selected carrier’s data network. And when we take it out, we can’t use that cellular network anymore. Well yeah, true. But, that’s just the basics.
What is a SIM card really? A SIM card is a small, tiny little chip (called a card, for lack of a better term), that you can insert into some smartphones. This card holds personal data with your selected carrier, basically allowing the carrier to identify your device and then turn on/off select services based on the plan you have setup with your carrier. If removed from the smartphone, your plan — and data — cannot be accessed (and therefore the phone can only be used, limitedly, on a WiFi network) until it’s put into another phone.
Now, the neat thing about SIM cards: that they give you some freedom when it comes to your phone. f you end up buying a new phone every now and then, and the SIM slot is the same size as on your original phone, then you’ll be able to simply insert your SIM card and use that as your primary phone, without having to get a new phone number, new data plan, and so on.
If SIM cards are so important for the phone companies to identify you, why do some use them and the others don’t?
GSM stands for “Global System for Mobile Communications,” while CDMA stands for “Code Division Multiple Access.” The difference between the two, in the simplest of terms, is the SIM card (for GSM networks) and the lack of a SIM card (for CDMA networks, although that’s changing). It’s worth noting that while Sprint and Verizon are considered CDMA carriers, they do offer SIMs in a limited sense on a newer LTE phones that will work just fine on any GSM network.
For GSM phones (or phones provided by AT&T and T-Mobile), you have to keep your SIM card inserted at all times in order to use your data, as your plan is tied to your SIM card. If you want to receive calls, the SIM card must be inserted. If you want to use your available data from your chosen plan while out and about, the SIM card must be inserted. However, you can use the smartphone for apps and internet when connected to a Wi-Fi network.
