When you're working on a shared Google Drive document, spreadsheet, or presentation, you often get lots of comments highlighting specific sections and pointing out things to change, fix, or work on. Previously, those comments would be condensed into an email and that was your only way of knowing someone has something new to say about one of your files.
Now, comment notifications will show up on the web as well as in all three Google apps. Docs, Sheets, and Slides already got a notifications setting in a previous update, but they'll now use that to also surface comments on your shared documents, just like in the screenshot above. You'll have to tap to read the entire comments if there are several and to reply or act on them.
The apps have been updated in the Play Store, but just in case they're not showing up for you yet, you can grab them from APK Mirror: