Am I the only one who finds Passbook incredibly confusing? It would make sense to me if I installed 'nodes' in it, for, say, American Airlines or whatever service I'm using. But the fact that I install separate apps and then it somehow works with those apps? Very confusing. It's like having a wallet that connects to a pocket full of loyalty cards rather than having them tucked away inside.
The Passbook passes work with the servers, not the client side app.
The apps allow you to download passes. But you can use websites and email to download them too.