> For the complete documentation index, see [llms.txt](https://sim-cards.learn-telecom.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://sim-cards.learn-telecom.com/gsm-identifiers.md).

# GSM Identifiers

- [Description](https://sim-cards.learn-telecom.com/gsm-identifiers/description.md): SIM cards have to main categories CDMA / GSM here i am focus on GSM SIM cards. This cards have two types of charging system PREPAID and POSTPAID.
- [ICCID - Integrated Circuit Card Identifier](https://sim-cards.learn-telecom.com/gsm-identifiers/iccid-integrated-circuit-card-identifier.md): The Integrated Circuit Card Identifier (ICCID) is a unique number that is assigned to each SIM card by the SIM card manufacturer.
- [SIM - Subscriber Identity Module](https://sim-cards.learn-telecom.com/gsm-identifiers/sim-subscriber-identity-module.md)
- [IMSI -](https://sim-cards.learn-telecom.com/gsm-identifiers/imsi.md)
- [Authentication key (Ki)](https://sim-cards.learn-telecom.com/gsm-identifiers/authentication-key-ki.md)
- [PIN2 - Personal Identification Number 2](https://sim-cards.learn-telecom.com/gsm-identifiers/pin2-personal-identification-number-2.md)
- [PUK2 - Personal Unblocking Key 2](https://sim-cards.learn-telecom.com/gsm-identifiers/puk2-personal-unblocking-key-2.md)