What is the difference between the present perfect and past perfect?

Related questions

1. What is present perfect and simple past?
2. What is the difference between simple present and present perfect?
3. What is present perfect tense for kids?
4. What is the form of present perfect simple?
5. What is the formula of simple present?
6. Why Is Present Perfect called that?
7. How do we use past simple?
8. What are simple present tense?
9. What are simple tenses?
10. How do you change Simple Past to Present Perfect?

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1. #happened
2. #future
3. #occurring
4. #example
5. #tense
6. #completed
7. #perfect
8. #present
9. #describe
10. #tenses
11. #writing
12. #recent
13. #refers
14. #still
15. #essay
16. #something
17. #finished