QR Codes are those square bar codes you see popping up on billboards and advertising. If you have a smart phone and download a QR reader application, you can take a picture of the QR code. The QR code will be converted to text. This might be a web page. It might be your business card or another advertisement. The concept is to take out your smart phone and snap a picture to capture all the information quickly without having to write anything down. QR codes are quite popular at trade shows for that reason. On my iPhone I use a free application from the Apple App Store called QR Reader for iPhone. It works great. If you Google QR Code Generator, you will find numerous on-line QR generators where you can select what you want such as a web page address or a business card or text. It will generate the graphic image that you can download and use.
QR codes don't work for people who don't have smart phones or haven't already downloaded a QR reader application on their smart phone. Also you have to be able to get a clear shot of the entire QR code square in the photo to be able to read the information.
I find QR codes can be quite useful.
This QR code is CSI's web page address https://www.csiny.com