What are tree conflicts in SVN?

Related questions

1. What is SVN head?
2. What is the difference between update to head and update to version in SVN?
3. What is head in github?
4. How do I find my SVN code?
5. What is SVN merge?
6. How does SVN solve tree conflict?
7. What does SVN resolve do?
8. What are tags in SVN?
9. What is a SVN number?
10. What is merge in SVN?

Tags

1. #directory
2. #files
3. #version
4. #content
5. #cannot
6. #conflicts
7. #structure
8. #recognizes
9. #known
10. #marked
11. #manifest
12. #which
13. #directories
14. #level
15. #before
16. #resolved
17. #since
18. #conflict
19. #rather
20. #committed
21. #victims