If you use Google Chrome as your internet browser/search engine, they have a couple of helpful features in the URL window.
Here's an example URL in a Google Chrome search window:
In the image above, you can click on the URL window (if you're using Google Chrome for your browser) and a QR code appears in the URL window. Click the QR code icon and a larger QR code appears. You can use the QR scanner app on your phone to scan the code and it will open this URL/website on your phone.
This is a simple help to let you open a desktop website on your phone. So if you're working on a desktop computer but want to send the link to your phone, you'll use this QR code in the URL window. You will need to have a QR code scanner app on your phone. Go to your phone's App Store and download a free QR code scanner.