The practice of comparing actual data with predicated data I order to ensure the veracity of a predictive model.
Optimizing a trading strategy on historical data and applying it to fresh data to see how well the strategy works.
Optimizing a moving average or trading strategy on historical data.
The process of designing a trading strategy based on historical data. It is then applied to fresh data to see if and how well the strategy works. Most technical analysis is tested with this approach.