Try to think of someone that you know who does not own a cell phone.
That’s right, pretty tough. And almost every new cell phone or smart phone these days comes with a built in camera. You can use them to take pictures, videos, and even chat live. Some in HD quality!
Researchers and marketers quickly caught on to this. This is when the QR code was born.
A QR code is a 2-D bar code in a square shape with smaller square symbols.
By now you probably have seen them in your mailbox, on posters and even in the grocery store. It looks like this:

Scanable by cell phones, these bar codes can do anything, and anyone can create them. For example, on our business cards we have a QR code for each employee. When scanned, it will add the employee's contact information to the persons' contact list.
Recently, QR have risen in popularity. Simply Google "QR code generator" and have hundreds of results returned.
Some companys like Marc Jacobs have even figured out how to manipulate them to start adding in special designs.
Sources
http://www.youthedesigner.com/2011/09/29/what-is-a-qr-code-and-how-does-it-work/
http://www.japantrends.com/en/wp-content/uploads/2009/06/marc-jacobs-qr-code.jpg