The Past Perfect Tense is used to describe an action that was completed before another action in the past. It is formed using "had" followed by the past participle of the verb. For example, in the sentence "She had finished her homework before dinner," the action of finishing the homework occurred before the action of having dinner. This tense helps clarify the sequence of events in storytelling or reporting. It emphasizes that one event happened earlier than another, providing a clearer timeline. For instance, "They had left the party when it started to rain" indicates that leaving occurred before the rain began.