Mobile phones with eSIM have a digital SIM card that's built into your smartphone. The eSIM is the successor to the physical, plastic SIM card. You can quickly and easily activate your phone plan via the app of your provider. On an eSIM, you can activate multiple phone plans and phone numbers at the same time. That way, you can keep your private and business messages separate. Going to travel outside the EU? You can buy a data bundle for that country at home and activate it when you arrive. That way, you're connected right away.