What is password entropy?

Related questions

1. Are passphrases secure?
2. Can you use spaces in passwords?
3. Why use a passphrase instead of a password?
4. What is a WPA password?
5. What is an example of a passphrase?
6. What is a passphrase for a printer?
7. How do password generators work?
8. What is a Diceware password?
9. Does Google allow spaces in passwords?
10. How many different passwords are possible with 4 digits?

Tags

1. #characters
2. #numbers
3. #using
4. #which
5. #length
6. #minimum
7. #selected
8. #character
9. #expansible
10. #symbols
11. #measurement
12. #uppercase
13. #based
14. #lowercase
15. #unpredictable
16. #entropy
17. #password