A SIM card, or Subscriber Identity Module, is a small removable card that stores information about your cellular network subscription, including your phone number, account details, and security settings. It allows you to connect to your carrier’s network and make calls, send messages, and use data services.
SIM cards are typically locked to a specific carrier, which means that they can only be used on that carrier’s network. However, it is possible to unlock a SIM card so that it can be used on any carrier’s network. This can be useful if you want to switch carriers or if you are traveling to a country where your home carrier does not have coverage.