It gives you more information about a product or will give you an app to their business.
We were looking at cars a few weeks ago and the dealership didn't have any prices on the cars, but if you scanned the code box, the window sticker with a price came up on my phone. I scanned the code at Texas Roadhouse and I got an app to the restaurant. You get the app on Itunes.
I think it's called a QR code - basically the code stores a website, or an app, etc. in the code, so that when you use your smartphone you can scan it, and go directly to the site (instead of having to write down the URL).