Ram Air Turbine. small fan which deploys into the airflow to provide electrical power generation.
Not quite - the 767 RAT drives a hydraulic pump, not a generator.
There is a hydraulic driven generator that can be used to generate electrical power if needed., however the RAT is primarily intended to provide hydraulics to the flight control surfaces in the event of a dual engine power loss.
BTW, the RAT is known to be extremely noisy when deployed.