The Rendering Statistics Window (Stats panel) can help confirm whether your game is suffering performance issues. In the first instance, your judgment about performance is normally based on whether you see a tangible problem in-game during testing. Afterwards, the Stats panel (such as the FPS statistic) can help confirm whether the identified problem really is related to game performance, as opposed to a scripting bug, or a software conflict. Nevertheless, the Stats panel can't tell you exactly what or where the problem is. To help track down the issue, you can use the Profiler window, which is accessible from the Unity editor menu, by navigating to Window | Profiler. Like the Stats panel, the Profiler measures game performance on the current hardware, that is, the system on which the editor is running:

Accessing the Unity Profiler from the application menu

The Profiler window initially appears as a free-floating window. For best results, consider docking...