The Rigidbody's resistance to changes in angular velocity (rotation).
Rotational inertia controls a Rigidbody's resistance to changes in angularVelocity. It is similar to how mass controls a Rigidbody's resistance to changes in linear velocity.
The rotational inertia is automatically calculated based on the Rigidbody's mass position relative to the centerOfMass. It can also be specified explicitly by setting this property in the same way mass can be set.