A Personal Unblocking Key (PUK) code is a security measure used to protect SIM cards from unauthorized access. If a user enters an incorrect PIN (Personal Identification Number) three times in a row, the SIM card will be locked and the PUK code will be required to unlock it.
The PUK code is typically provided by the mobile network operator when the SIM card is purchased. It is important to keep the PUK code safe and separate from the PIN code, as entering an incorrect PUK code 10 times in a row will permanently block the SIM card.