static Rotation LookAt( Vector3 forward, Vector3 up )

Summary

Create a Rotation (quaternion) from a forward and up vector

static Rotation LookAt( Vector3 forward )

Summary

Create a Rotation (quaternion) from a forward vector, using Vector3.Up as an up vector. This won't give nice results if ['paramref'] is very close to straight up or down, if that can happen you should use Rotation.LookAt.