Passbook is one of the flagship additions to Apple's mobile operating system in the iOS 6 update. It's also been , as Apple had offered few specifics prior to Wednesday's iOS 6 on how exactly the feature would work.

That changed Wednesday night when MLB Advanced Media, the interactive media arm for Major League Baseball, announced that four teams would support ticketing through Passbook. Fans attending games for the San Francisco Giants, New York Mets, Boston Red Sox, and Kansas City Royals will be able to store electronic tickets on their iPhones and iPod touches and use them to attend home games for the rest of the 2012 season.

I had the chance to see Passbook in action Wednesday night, as MLB Advanced Media showed off the service at a San Francisco Giants home game. Here's what you can expect from this new addition to iOS 6--at least if you and your iPhone are heading out to a ballgame.

Because Passbook is such a new feature, this is the first ticket I've used through the app, and I found using Passbook to be really easy and straightforward. After receiving an e-mail confirmation about my ticket purchase, I opened the e-mail in Mail on my iPhone, then I tapped a link that read "Click here Add to Passbook." From there, Passbook launched to reveal a bright orange ticket. Tap the small Info button in the bottom right corner to flip the ticket over, which shows the venue address and phone number, along with the ticket's terms and conditions, and a toggle switch to show your ticket on the Lock Screen. (Passbook is aware of your location, so that tickets, cards, and coupons can appear on your lock screen when you arrive at the appropriate venue.)

When I got to AT&T Park, my Passbook ticket was scanned just like a regular (paper) ticket. I was then issued a small paper receipt as a backup in case my iPhone ran out of juice, and for something easier to show as a proof of purchase. It's recommended that you keep the receipt until you exit the ballpark.