How does a message authentication code work?

Related questions

1. Is sha512 better than sha256?
2. What is Entity Authentication?
3. What are the message authentication functions?
4. How does an HMAC work?
5. What is required by the Advanced Encryption Standard?
6. How is an HMAC different than a hash?
7. What is SHA HMAC?
8. How does Hmac provide authentication?
9. What is the most secure hashing algorithm?
10. How good is AES 256 encryption?

Tags

1. #short
2. #sometimes
3. #information
4. #confirm
5. #stated
6. #piece
7. #changed
8. #authenticate
9. #known
10. #cryptography
11. #other
12. #words
13. #authentication
14. #message
15. #authenticity
16. #sender