Update, FixedUpdate

참조 : https://www.youtube.com/watch?v=ZukcUv3pyXQ

Update()
> Called Every Frame
> Used for regular updates such as :
    Moving Non-Physic objects
    Simple Timers
    Receiving Input
>Update interval times vary

FixedUpdate()
> Called Every Physics Step
> Fixed Update intervals are consistent
> Used for regular updates such as:
   Adjusting Physics (Rigidbody) object