An eSIM is a SIM card built into your phone that you activate by downloading a profile, no plastic, no shop. Here's what that means for travel.
A traditional SIM is a tiny plastic chip you slot into your phone. An eSIM ('embedded SIM') is that same chip, soldered permanently inside the device. Instead of swapping plastic, you download a carrier 'profile' onto it, one QR scan or a single tap, and your phone is on a new network.
Because activation is just a download, you can buy a data plan for your destination before you leave home, install it on Wi-Fi, and land already connected. No airport SIM kiosks, no queues, no paperclip over a SIM tray. Your home SIM stays exactly where it is, so you keep your number.
A travel eSIM is data-only: it carries your internet, not a phone number. Calls and texts keep working on your home number, and apps like WhatsApp work over data as normal. One profile installs once, on one device, and can't be moved, so you buy one per phone, and top it up rather than reinstalling.