From bitsofcode: https://bitsofco.de/using-aria-live
<main> section of the page is a search form. But, when you type in a query such as “css” and search, several articles related to that term begin to appear on the page.
If you are looking at the page, it is obvious when the articles appear because you can see the content change. However, if you’re using a screen reader, there is no way to tell exactly when this happens. The
aria-live attribute allows us to tell assistive technology what parts of the page are likely to change. With this information, it can listen for changes to those particular elements and notify the user of any updates made.