eSIM or embedded SIM is a so called Universal Integrated Circuit Card (UICC) which replaces the old removable SIM card. Basically the UICC is an embedded programmable SIM card to which consumers can remotely download a wireless operator's SIM application.
In other words, instead of having to go to your wireless operator's physical shop, purchase a SIM card and insert it into your wireless device, you are now able to scan a QR code, follow the steps and install your service remotely. Moreover, these programmed SIM applications can be removed and replaced with new ones in the case of switching wireless providers. Here is a video by GSMA explaining how eSIM works in a very accessible way.
In another article we discuss International SIM Cards and how, for the past 20 years or so, international travelers have been able to substantially reduce costs associated with voice and data communication.
eSIM technology can be used in the same way, but without having to order a physical SIM and inserting it into a mobile device. Moreover, there are some new companies such as HolaFly, specializing in data only eSIM services. Nowadays data access is enough for many people to stay in touch or use maps and other smartphone apps.
The standard has been widely adopted by wireless providers across the world in the last few years. The list of compatible phones has also been growing, although some phone makers have only been installing this feature on higher end models.