Standard Google Maps uses a top-down or angled camera. A simulator hijacks this. It places a "camera" at bumper height (approx. 3-4 feet off the ground) inside the 3D world. As the camera moves, the API fetches new tiles.
Imagine a truck driver who has never been to downtown Boston. Before they leave the depot, they spend 15 minutes driving the route in a Google Maps 3D simulator. driving simulator google maps 3d
If you want to try this today, here are the leading platforms bridging Google Maps 3D and driving. Standard Google Maps uses a top-down or angled camera