Google Photos introduced archives a long time ago, but I have to admit that I don't use the option often. I take a ton of screenshots and I'm used to just going to the Photos app on my phone and deleting them completely as there's no point in me keeping them. However, if you don't do that or if you forget to archive some quite unnecessary pics, Photos will remind you to do so, and that reminder is showing up on the web interface as well.
We're not sure how new this pop-up is, but a couple of readers told Artem that they only started seeing it a few days ago, so we're inclined to think it's relatively recent. If you head over to photos.google.com and find a screenshot in your collection, open it and you should get this small pop-up up top to archive it. You can instantly click to archive the photo or check the help "?" button where Photos explains that archiving works well for screenshots and receipts. They'll still be searchable and will show up in albums, but they won't litter your photo library.
I've only tested it with screenshots as I don't have any receipts in my photo library, but do let us know if you spot the same pop-up for receipts or other kinds of photos as well.
As I suspected, Photos shows the archive prompt for other kinds of photos too. It works for receipts, shipping labels, product/shopping labels, and different kinds of documents. Thanks to everyone who pointed these out!