VAG vehicles, including Audi, Volkswagen, Seat, and Skoda, use EEPROM chips to store various vehicle settings, configurations, and calibration data. EEPROM (Electrically Erasable Programmable Read-Only Memory) is a type of non-volatile memory that can be electrically programmed and erased.

A VAG EEPROM programmer is a tool used to read, write, and modify the data stored in the EEPROM chip. This programmer is usually a small device that connects to the vehicle's OBD-II port or directly to the EEPROM chip.

The "120" in your search query might refer to a specific device or programmer, such as the VAG EEPROM Programmer 120. This device is likely a popular tool among VAG enthusiasts and technicians, allowing them to program and modify EEPROM data in various VAG vehicles.

Here's a detailed overview: