What is an eSIM?
A SIM that is built into your phone and set up by scanning a code.
A SIM without the plastic
A SIM is what tells a mobile network who you are. For years it was a small plastic card. An eSIM does the same job, but it is a chip built into the phone, and the carrier details are downloaded onto it instead of being slotted in.
You add one by scanning a QR code or entering an activation code. There is nothing to post and no tray to open.
Why it matters for a backup line
Most recent phones can hold more than one eSIM and keep two lines active at the same time. That is what makes SecondBars possible: your existing line stays where it is, and SecondBars is added as a second one next to it.
Good to know
An eSIM stays on the phone until you remove it. If you delete it by mistake you will usually need a new code to add it again, so only remove it if you mean to.
Keep your carrier and your number.