Your smartphone is a highly advanced piece of modern technology, jam-packed with Wi-Fi, GPS, a brilliant camera, Bluetooth, motion sensors and much, much more. To make calls, use mobile data and send cellular text messages, you’ll still need to insert a SIM card to connect with your network operator. SIM stands for Subscriber Identity Module. SIM cards are effectively mini circuit boards which identify your service provider and your mobile phone number.
There are actually five types of SIM cards (from largest to smallest):
✦ Full-size SIM (FF): This is the huge, outdated credit card-like SIM card that used to fit into much larger phones. This type of sim card is not supported by the mobile phone market anymore since 2016.
✦ Mini-SIM (2FF): Still, this SIM type is outdated. It is significantly smaller than the full-size SIM, but it is still pretty large for today's standards. Usually they are more prevalent on older basic phones and EDGE/3G smartphones. The 1st gen. iPhone through the iPhone 3GS all used mini-SIM.
✦ Micro-SIM (3FF): Most manufacturers are now moving smaller than micro-SIM to nano-SIM, but some phones and tablets still use micro-SIM. Micro-SIMs are used in a wide range of different devices, eg 3G to 4G, LTE, GSM devices.
✦ Nano-SIM (4FF): Now this is the current type of SIM card. Most devices that are coming out now are using nano-SIM. The first phone to use nano-SIM was the iPhone 5, and all iPhones as well as iPads from the iPhone 5 on and the iPad mini on use nano-SIM, respectively.
✦ Embedded SIM: The SIM card would be built-in to the device and act as a subscriber module from there. Currently, only one device has embedded SIM, and that is the new 9.7-inch iPad Pro. That device does also have the obligatory nano-SIM slot as well, just in case you might need it.