what is esim card
Definition: SIM Card â SIM is short for Subscriber Identity Module. SIM cards are small removable smart cards that are used in many cell phones to store data like a customer's mobile phone number, the mobile phone company they use, and address book information.ome phones have what is called a SIM lock, a feature that uses the SIM to tie the mobile phone to a specific phone company (usually the one who the user bought the phone from originally).