I am learning how to create them: you just need an extension in Chrome - it is called Quick QR Code Generator.
You right-click on the webpage you want to share and then you generate the code, you download the code and embed it in your blog/website.
Here is the QR Code for my second blog where I write posts about the use of technlogy or my experiences online as an educator:
Here you can see the QR Code for a post which I have just written for the students I am teaching for CAMBRIDGE ENGLISH EXAMS: it is about writing an essay
Why using QR Codes? It is simple and you can create materials online, share weblinks and get your learners engaged. Students can work with their smartphones and you can share a lot of documents and materials.
I am going to continue learning about QR Codes and will post about it in the next days.