First, navigate to your home screen. Then, find the Camera app and open it. The only thing you want to be mindful of here is that you are using the "photo" option.
Simply point your camera at the QR code (no need to take a picture of the code), and you will notice a notification will appear at the top of your screen. You can then click on that notification to be routed to the source of the information (the link to whichever website or app).
In my case, it was a catalog for cat products, where I could see all the recent sales and use the coupon I received via mail. And... that was it. You're done!
Sometimes, when you are busy or out and about and your iPhone starts ringing, you don't want to pick it up, but you know it might be so-and-so with that important call you've been waiting on.