What is the different between key password?

You need the password to the key to publish. The "keystore" is basically a file that can hold multiple keys, and is password protected. So, the top left password is to open the key store, and the other two are the passwords to the key itself within the store. So, the same keystore might be used between multiple projects, but the key itself will only work for one project.

As far as I know, there is nothing preventing you from using the same password for both, however.