Although the ability to search for text in photos is new, it’s been possible to find photos based on locations, people, and objects since iOS 10. However, until now, you’ve had to go into the Photos app to do that (or ask Siri).
With iOS 15, Apple is adding the entire Photos library to the main Spotlight search, so your photos will appear when doing a system-wide search. This means you can search by people, scenes, elements, location, and even text in photos.
This will be particularly useful for looking for things like recipes, handwritten notes, and receipts, where you may not realize off-hand that the details are in a photo, as opposed to an email, messages thread, or note.
Spotlight will also provide rich results for contacts, so when you search for a person you’ll not only get quick access to call, message, or email them, but also location details, recent messages and email conversations, shared photos, calendar appointments, notes, and even files.
Similarly, searching for an actor, musician, TV show, or movie will also return much more detailed results right in the Spotlight view.