SIM stands for Subscriber Identity Module. It is a plastic card with a computer chip that, when activated and slotted into a mobile device, contains the user’s information required to connect to a mobile network.
An eSIM, or embedded SIM, is a more convenient and smarter form of a SIM card, which eliminates the need for a physical chip (good for the environment!) An eSIM is managed through the network and can be updated over the air. Most new devices on the market are eSIM compatible.