They were around for a while but never took off. Now they are and being used everywhere and if you aren’t well, you need to be.
They are good for a variety of thing because they can be used to code just about anything. Most use them for advertising which makes it easy to track ads. You create a QR Code for a landing to a particular page. Watch which page gets the most hits and bingo you know which ad works best.
They can also be used to send other messages. You can make them into coupons. My favorite use as it’s the most effective is to make one for Google Map Reviews. A smart business knows Google maps and reviews mean business. So instead of having someone type in some URL or search and review you, give them a QR Code.
You can also make Plain text and other kinds of QR Codes usually for free. Ones like this one.
The easiest place to make them that I have found is https://www.the-qrcode-generator.com/