Apple's Find My app enables you to track your friends and family's location. The person you want to track has to have an iPhone too, and they have to accept your request to share their location with you, but once setup, you can track your family or friend's iPhone at any time.
Original source: https://www.pocket-lint.com/how-to-setup-find-my-friends-track-an-iphone-plus-tips-and-tricks/
