Two examples I know off the top of my head is
1)
If you take the same route regularly, charge your device in specific locations or just are at certain places a lot, it will be able to determine your home and work/study place automatically from this behaviour, so when you leave the house in the morning it can say “15 minutes to work with light traffic” or whatever without any user input
2)
If you open the Photos app, you can search the photos by content. Like writing “cat” or “mountain” and it will show relevant images without ever needing to manually tag the images; Machine learning identifies what’s on the images and tags them for search automatically