A good example is the image tagging in Photos which has been there for quite a while, if you search for a term in your images folder it'll show you images they

A good example is the image tagging in Photos which has been there for quite a while, if you search for a term in your images folder it'll show you images they classified with that term. This applies regardless of if you are using iCloud or not as the classification is performed locally, keeping your images on your device as opposed to sending them off to be classified on a server somewhere.