official from apple (owh.. they will release os 6 too) :
Your boarding passes, movie tickets, retail coupons, loyalty cards, and more are now all in one place. With Passbook, you can scan your iPhone or iPod touch to check in for a flight, get into a movie, and redeem a coupon. You can also see when your coupons expire, where your concert seats are, and the balance left on that all-important coffee bar card. Wake your iPhone or iPod touch, and passes appear on your Lock screen at the appropriate time and place — like when you reach the airport or walk into the store to redeem your gift card or coupon. And if your gate changes after you’ve checked in for your flight, Passbook will even alert you to make sure you’re not relaxing in the wrong terminal.