For years, this chip was on a physical card that you could swap in and out by ejecting a SIM card tray from your phone. Most modern phones, however, also support eSIM.

Googling so far leads me to believe that my existing data plan is iphone only...so when I put the iphone sim card into the android phone, data won't work.

Have you ever wondered exactly how a SIM card works? We'll help you understand why your phone needs one and what they do to keep you connected.