SIM: Subscriber Identity Module
SIM stands for Subscriber Identity Module or Subscriber Identification Module. It is actually an electronics integrated circuit(IC) used to store the subscriber Identity number. These electronics can store mini information. For example, we can store our contact number and text messages to SIM cards. SIM cards can be used only in GSM mobiles.
The first SIM card was developed in 1991 by Giesecke & Devrient.