What defines the past perfect tense?

The past perfect tense is used specifically to indicate that an action was completed before another action took place in the past. This tense provides clarity about the sequence of events, establishing a timeline for when these actions occurred. For instance, in the sentence "She had finished her homework before dinner," the use of the past perfect "had finished" shows that finishing the homework was the first action completed, followed by the second action of having dinner. This highlights the relationship between the two past actions and is essential for conveying accurate chronological order in narratives.