Does the iPhone have a built-in GPS so that it can tell Google Maps where it is?
No. Just like on your computer, you have to tell Google Maps where you are and where you’re going. But Apple has made it easy to follow along with driving directions by adding a simple pair of previous/next turn buttons that let you quickly step from intersection to intersection as you complete your journey. However, if you’re expecting your iPhone to tell you to turn right in 100 feet, you’ll be disappointed.