What does u1 and u3 mean?

Related questions

1. How many pictures will 64gb hold?
2. How much 4k can 64gb hold?
3. What is Micro SD UHS 1?
4. What's the highest GB SD card?
5. What is a Class 4 SD card?
6. Which memory card is better Class 4 or 10?
7. Is class 10 the same as UHS 1?
8. How many hours of 1080p video can 64gb hold?
9. What does u3 mean on an SD card?
10. What is UHS I u3?

Tags

1. #means
2. #newer
3. #whereas
4. #transfer
5. #minimum
6. #signifies
7. #guaranteed
8. #designation