Embedded SIM, often known as eSIM. It is a SIM card that is pre-programmed into a phone without having to insert it manually. It works the same way as a physical SIM card, but it doesn’t require a physical card and can only be used on devices with eSIM compatibility pre-installed.
It could not be very pleasant for those who thought Mi A2 came with the eSIM capability. There’s no eSIM-capable program pre-install on this phone.