This new ability is part of the iPhone's Visual Lookup system, which can currently identify things like plants, as well as let you remove the background from photos with an obvious subject.
In iOS 17 it's also gaining the ability to make stickers for use in messaging apps, search for recipes related to a pictured dish, translate diagnostic lights on your car's dashboard and now help with your laundry.
As with the car warning lights, the iPhone is reading the washing information from the ISO website, the organization in charge of standardizing these symbols across the world.
Users will get a small description of what the symbol means in the Visual Lookup window, but you can tap any of them to open up the source page in Safari if you want to double-check what you're doing before you put precious items of clothing in the washing machine or dryer.
There are of course already guides to laundry symbols you can consult, but being able to show information only for the relevant symbols is certainly useful. Your iPhone can't set your washer or dryer for you (at least not yet), so it's still good to check what the symbols translate to on your particular appliance. Don't just rely on the quick wash setting!
iOS 17 isn't out yet for the average user with a compatible iPhone in hand. Right now it's in developer beta, with a public beta likely to arrive in the next few weeks going by Apple's historic launch timings.
The stable release, a.k.a. when most people will actually be able to download and try out all of the best iOS 17 features, won't be until September or so. We can comfortably predict this because Apple usually ties the release to the latest iPhone launch, which will be the iPhone 15 this time around.