Fly mode is like flying a drone around the scene. You have full 3D freedom and are not stopped by any geometry, allowing you to explore every detail from any angle.
Orbit mode allows you to easily inspect an object by rotating around a central point. Use your mouse to view the object from all sides and distances.
Measuring mode lets you measure distances in 3D space and calculate the area of closed loops.
Active Indicator: Once measuring is activated, you will see an indicator at the top of your screen showing that measuring mode is active.