Donald Trump Jr. and Eric Trump have launched Trump Mobile, a new family venture featuring a 'bring your own phone' data plan. The SIM card and its services, which are part of 'The 47 Plan,' cost $47.

A SIM card, or subscriber identity module card, is essential component of any phone. It connects your device to a cellular network and stores vital information, including your phone number.

These two ways of connecting your phone to a cellular network are very different. We tell you about each and how you can switch from one to another.

With eSIM availability expanding, the SIM card tray might eventually be removed from iPhones sold outside of the U.S., but for now it lives another year. Thanks, Apollo Zhao!