Can do this entirely mathematically - no physics
When the ball gets to a certain cartesian point (e.g. 5 or -5) it is to go in the opposite direction
Everything in Unity happens one thing at a time - the more you want it to do, the longer it takes. If frame rate is dropping, there's too much logic going on in the code
void - "fire and forget" the code will do it's thing and be finished; return - when you want to see a result of the function e.g. an integer from the internal math. A vector is like a set of coordinates for the code