An eSIM, or embedded SIM, is a digital SIM that allows devices to connect to a mobile network without needing a physical SIM card. This technology offers the convenience of being able to switch between mobile network providers without having to physically swap out SIM cards. It's particularly useful for devices like smartwatches, tablets, and laptops that may not have space for a traditional SIM card. eSIM technology can support multiple profiles, enabling users to have more than one phone number on a device.