Testing with an editor remote tool
Developers have been using Unity for many years to develop games and applications for iOS and Android devices. You want the ability to click Play in the Unity Editor and run the current scene remotely on your attached mobile device. Having an iterative develop-test-update-repeat cycle is key to more efficient and effective development.
To facilitate this developer workflow, Unity provides an application called Unity Remote 5 that you install on your phone and then connect to the Unity Editor. It is available for both Android (https://play.google.com/store/apps/details?id=com.unity3d.mobileremote) and iOS (https://apps.apple.com/us/app/unity-remote-4/id871767552). It allows you to use a mobile device to view and test your project live, inside the Unity Editor, without having to build each time. The device acts as a "remote control" for the scene running in the Editor Play-mode, including screen touch, accelerometer, gyroscope, and webcam...