What is the difference between past perfect and present perfect?

Related questions

1. What's the difference between simple past and past perfect?
2. What is the rule of Past Perfect?
3. What is the past perfect simple in English?
4. What is the difference between simple past and past progressive?
5. What is rule of past perfect tense?
6. Has stolen or stole?
7. How do you change past simple to Past Perfect?
8. How do you use past perfect?
9. What is the difference between past and earlier past?
10. What is the rule of past perfect continuous?

Tags

1. #difference
2. #event
3. #combining
4. #events
5. #present
6. #because
7. #participle
8. #ended
9. #started
10. #between
11. #specified
12. #similar
13. #formed
14. #perfect
15. #however