TVA generally refers to the Throttle Valve Actuator and its associated control strategies.
On petrol engines, the throttle is one of the main components used to control engine load.
On diesel engines, the throttle valve can have a different purpose.
It may be involved in:
EGR control,
airflow management,
engine shutdown behavior,
intake pressure management.
So the same TVA label can represent different functions depending on the engine and ECU.