Shadow file

Just a quick question- forgive me if it is dumb- but here it goes:

In the shadow file what does it mean when the password hash is just a " !! " ?

With all those default users that were installed with Linux- I couldn't help but wonder, I assumed for I while that it prevents that user from loging into a shell- but I'd like a sure answer. Thanks.

Basically it means that the passwords are in another file and that the file you are viewing is shadowed. If you already knew that then sorry for this waste of a post.

It is the shadowed file that I am looking at in this case- the only two users with password hashes are root and my own user- all the rest are !! or *