What is present perfect past perfect and future perfect?

Related questions

1. What is present perfect and present perfect continuous?
2. What is present perfect aspect?
3. What is the structure of present perfect continuous?
4. When we use present perfect continuous tense?
5. Why we use present perfect continuous tense?
6. Where do we use present perfect tense?
7. What is present perfect tense and past perfect tense?
8. What's the difference between past perfect and present perfect?
9. What is the identity of present perfect tense?
10. What is present perfect tense in German?

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