What does making a skill Legendary do in Skyrim?

Related questions

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2. What happens if you don't kill Cicero?
3. How many times can you legendary a skill in Skyrim?
4. Is Stalhrim armor better than daedric?
5. Is Stalhrim better than Dragon Bone?
6. Can you unlock every perk in Skyrim?
7. Will a horse run until it dies?
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Tags

1. #gained
2. #longer
3. #skills
4. #character
5. #legendary
6. #skyrim
7. #again
8. #levels
9. #increasing
10. #leveling
11. #reach
12. #contribute
13. #skill
14. #occurs
15. #allow
16. #purpose
17. #level
18. #making