The “QR” part of “QR Code” stands for “Quick Response.”
And the “Code” part is basically a new language that only your smart phone (or tablet) can understand.
The little dots and lines (pixels) contain information that comes together like “morse code” for your smart phone’s camera.
Your camera decodes the information and displays a link to a website or other resource that you can tap on to see what the “QR Code” maker wanted you to see.