how do you use passbook

I recently purchased my iPhone 5 and i love it. However, i can't seem to get passbook to work. I downloaded all the apps and setup accounts on all the apps and whenever i open it, it either goes to the default starter screen or takes me to the app store to download the apps i have already downloaded.

Example: I downloaded the Target app, created a login for Target and i also have a Target gift card. Isn't passbook suposed to do something whenever i go to target? I am going to Target today and i brought the gift card with me because at this point i do not believe passbook will do anything.

Thanks.