vagcom-eewritelang is a command line instruction used to force the VAG-COM interface to write raw hexadecimal (HEX) data directly to the EEPROM chip of a control module, bypassing the standard "Adaptation" GUI.
The ECU receives this data and must store it. It cannot store it in RAM, or the setting would vanish when you lock the car. It writes it to the EEPROM. This is the ee-write action. vagcom-eewritelang