Определение и Значение "past perfect progressive"

What is the "past perfect progressive"?

The past perfect progressive is a verb tense used to describe actions that were ongoing in the past before another past action occurred. It emphasizes the duration of the first action up to a specific point in the past. It is formed by using "had been" followed by the present participle of the main verb, which typically ends in "-ing." For example, in the sentence "She had been working at the company for five years when she decided to leave," the phrase "had been working" indicates that the action of working started before another past action, which is her decision to leave. The past perfect progressive is useful for providing context and highlighting the continuity of actions prior to a particular moment in the past.