Photorealistic 3D Tiles are map tiles that contain Google's 3D geodata in the OGC 3D Tiles format. You can render Google's 3D maps with your own 3D Tiles renderer, or you can use an open source library for 3D geospatial visualization.
Why use 3D Tiles?
Google offers 3D Tiles for next-generation visualization use cases. You can use 3D Tiles to build stunning 3D perspective views, just as you can with Google Earth. These views help your users better understand geographic context, improve how they navigate, and they can showcase a place for storytelling. Using a renderer of your choice, you can also smoothly maneuver your camera through a scene to view it from different angles.
Review the Map Tiles API's coverage. Google regularly updates and adds imagery.