An embedded SIM, or eSIM, replaces the traditional plastic card with a small chip built directly into your device. When you subscribe to a mobile plan, your carrier sends a secure digital “profile” (often via QR code or app) which downloads to the chip and enables network service. 

The process works like this: your device’s eUICC (embedded Universal Integrated Circuit Card) stores multiple operator profiles, and a remote provisioning system handles authentication and activation. From the user side, it’s as simple as scanning a code, tapping install, and you’re connected - no need to swap physical cards. 

This technology brings convenience: switching carriers or installing travel plans becomes faster; devices can be slimmer and more secure. However, it also means your SIM identity is tied to that embedded chip, so migrating to another device or switching systems may require carrier support. 

In short: eSIM is the digital evolution of SIM cards - making connectivity smoother, more flexible, and more embedded in the tech you already use.