When you set up WordPress, you put your database settings in the wp-config.php file. There is a new line there:
// Change SECRET_KEY to a unique phrase. You won’t have to remember it later,
// so make it long and complicated. You can visit https://www.grc.com/passwords.htm
// to get a phrase generated for you, or just make something up.
define(‘SECRET_KEY’, ‘put your unique phrase here’); // Change this to a unique phrase.
While I’m not sure what the “secret key” is used for, I prefer using my own pass phrases and passwords. I generally use the pwgen program to generate my passwords. This command
pwgen --numerals --capitalize --symbols --secure 64
entered in my PowerBook’s Terminal gave me a good password. You can install pwgen for OS X with these instructions: Building pwgen on Mac OS X. Why use pwgen over grc.com? Why not? It’s good to have options.