The word “QR Code” is a registered trademark of DENSO WAVE INCORPORATED in Japan and other countries.
Here you can create QR codes based on the PHP QR Code library. With QR code readers, which are installed on some mobiles or are available as separate applications you can read such codes.
See also: “QR code” at Wikipedia, ZXing Barcode Scanner (Android)
If you want to use the generated QR code on your own website, please download the image and is use a local copy of it and do not link to the generated image here – thank you!