In terms of the functions of these 2 tenses, I should say that we use present perfect tense to refer to an action that started in the past and either the results of that action or the action itself continues to the present time or it has reached for the present time and it might continue into the future. For example:
This house has been vacant since 2010.
The above sentence means that the house is still vacant.
Past perfect tense is used to refer to an action that occurred before another action in the past, and therefore, it cannot reach the present moment. For example:
When I arrived home, the thieves had already stolen everything.
In the above sentence, 2 actions occurred in the past:
1. arriving home
2. stealing everything
We put the older action in the past perfect tense.
For more information about present perfect tense, study this article.
Last updated on June 12, 2022 by Dr. Mohammad Hossein Hariri Asl